diff --git a/22/Cargo.lock b/22/Cargo.lock
index 385c3c7..be7ab4d 100644
--- a/22/Cargo.lock
+++ b/22/Cargo.lock
@@ -14,6 +14,7 @@ version = "0.1.0"
 dependencies = [
  "itertools",
  "ndarray",
+ "petgraph",
 ]
 
 [[package]]
@@ -22,6 +23,34 @@ version = "1.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a26ae43d7bcc3b814de94796a5e736d4029efb0ee900c12e2d54c993ad1a1e07"
 
+[[package]]
+name = "equivalent"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
+
+[[package]]
+name = "fixedbitset"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
+
+[[package]]
+name = "hashbrown"
+version = "0.14.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
+
+[[package]]
+name = "indexmap"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d530e1a18b1cb4c484e6e34556a0d948706958449fca0cab753d649f2bce3d1f"
+dependencies = [
+ "equivalent",
+ "hashbrown",
+]
+
 [[package]]
 name = "itertools"
 version = "0.12.0"
@@ -82,6 +111,16 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "petgraph"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1d3afd2628e69da2be385eb6f2fd57c8ac7977ceeff6dc166ff1657b0e386a9"
+dependencies = [
+ "fixedbitset",
+ "indexmap",
+]
+
 [[package]]
 name = "rawpointer"
 version = "0.2.1"
diff --git a/22/Cargo.toml b/22/Cargo.toml
index 6ac632a..75be33d 100644
--- a/22/Cargo.toml
+++ b/22/Cargo.toml
@@ -8,3 +8,4 @@ edition = "2021"
 [dependencies]
 itertools = "0.12.0"
 ndarray = "0.15.6"
+petgraph = "0.6.4"
diff --git a/22/input b/22/input
deleted file mode 100644
index 92d2852..0000000
--- a/22/input
+++ /dev/null
@@ -1,1300 +0,0 @@
-2,1,68~2,3,68
-6,9,174~6,9,174
-7,5,106~7,7,106
-0,4,227~0,5,227
-7,0,225~9,0,225
-1,4,66~1,4,67
-9,5,189~9,6,189
-5,0,48~8,0,48
-2,3,92~2,4,92
-2,0,290~4,0,290
-6,6,117~6,8,117
-4,0,288~4,3,288
-3,3,210~3,3,212
-1,0,7~4,0,7
-3,1,111~4,1,111
-0,8,261~3,8,261
-8,1,65~9,1,65
-4,1,174~7,1,174
-0,4,103~0,6,103
-2,0,222~3,0,222
-7,5,130~7,7,130
-7,6,135~7,7,135
-5,1,57~6,1,57
-2,1,204~2,4,204
-5,1,235~5,3,235
-2,4,185~3,4,185
-3,8,36~3,9,36
-6,6,121~6,6,121
-7,3,49~7,5,49
-5,5,80~9,5,80
-5,3,83~5,6,83
-1,1,172~3,1,172
-6,2,277~7,2,277
-7,2,111~7,4,111
-5,6,191~5,9,191
-2,4,157~2,5,157
-1,6,127~3,6,127
-2,2,287~2,4,287
-7,3,279~7,3,282
-4,1,298~4,3,298
-6,1,97~8,1,97
-1,8,112~1,9,112
-5,1,207~7,1,207
-9,4,45~9,6,45
-7,0,289~7,2,289
-9,1,130~9,2,130
-5,2,142~8,2,142
-7,8,88~7,9,88
-6,4,95~6,8,95
-4,6,267~7,6,267
-6,5,243~6,7,243
-4,7,198~4,9,198
-8,6,205~8,8,205
-5,1,185~5,3,185
-6,4,149~6,6,149
-2,7,236~4,7,236
-3,0,180~3,3,180
-0,2,129~2,2,129
-5,5,123~5,5,124
-2,1,135~2,1,137
-3,3,92~5,3,92
-3,3,83~3,5,83
-4,7,17~4,9,17
-5,5,201~5,5,201
-6,5,233~6,5,235
-6,0,81~6,1,81
-8,2,36~8,3,36
-3,4,160~3,6,160
-8,4,233~8,6,233
-0,6,55~0,9,55
-6,8,108~6,8,108
-9,5,280~9,9,280
-8,1,61~8,2,61
-5,9,32~7,9,32
-6,0,82~9,0,82
-0,2,84~0,3,84
-8,6,242~8,9,242
-1,4,64~3,4,64
-7,0,47~7,2,47
-8,0,85~8,2,85
-1,2,197~1,5,197
-6,5,92~6,6,92
-5,0,162~5,3,162
-8,1,245~8,1,247
-1,8,102~4,8,102
-1,7,263~3,7,263
-8,3,35~8,6,35
-0,2,225~0,5,225
-2,0,140~5,0,140
-4,9,192~7,9,192
-2,4,94~2,7,94
-1,7,26~1,7,27
-4,2,75~4,4,75
-0,9,109~2,9,109
-7,5,234~8,5,234
-7,5,79~7,8,79
-5,1,240~7,1,240
-0,1,167~0,4,167
-2,3,183~4,3,183
-9,4,64~9,7,64
-3,8,90~4,8,90
-7,2,268~7,4,268
-6,4,50~7,4,50
-4,6,268~4,9,268
-8,2,136~8,2,136
-2,4,51~4,4,51
-0,0,182~0,1,182
-1,2,215~4,2,215
-3,2,204~3,4,204
-6,4,42~6,6,42
-1,7,271~1,9,271
-3,1,93~3,3,93
-7,8,229~9,8,229
-4,5,51~4,7,51
-8,1,62~8,3,62
-9,4,259~9,7,259
-9,1,117~9,3,117
-4,9,272~6,9,272
-7,7,61~9,7,61
-7,7,277~9,7,277
-0,8,274~3,8,274
-8,2,141~8,3,141
-5,6,175~5,8,175
-0,7,148~1,7,148
-8,1,269~8,3,269
-8,0,88~8,2,88
-6,0,135~8,0,135
-9,3,245~9,6,245
-5,4,159~5,7,159
-0,5,26~2,5,26
-0,8,166~1,8,166
-1,7,249~5,7,249
-0,4,229~2,4,229
-9,7,12~9,9,12
-6,4,273~6,6,273
-5,1,151~5,1,155
-3,6,94~4,6,94
-4,7,245~4,7,245
-8,5,38~8,7,38
-9,4,91~9,6,91
-3,2,159~3,3,159
-5,1,94~6,1,94
-5,3,182~5,4,182
-2,7,125~4,7,125
-5,4,85~5,4,87
-5,2,109~5,5,109
-4,0,1~5,0,1
-5,6,33~7,6,33
-8,5,119~9,5,119
-0,4,241~0,6,241
-6,0,204~6,3,204
-9,1,223~9,2,223
-1,4,215~3,4,215
-2,1,178~4,1,178
-6,5,28~6,8,28
-2,0,154~4,0,154
-0,5,5~0,7,5
-6,9,176~8,9,176
-8,2,114~8,4,114
-3,6,53~4,6,53
-9,6,216~9,6,216
-3,0,12~4,0,12
-1,3,154~1,3,156
-3,2,4~5,2,4
-5,5,105~5,7,105
-9,2,32~9,4,32
-6,2,175~6,3,175
-7,3,100~9,3,100
-2,9,244~4,9,244
-7,1,217~9,1,217
-1,2,121~1,6,121
-5,9,217~7,9,217
-7,4,183~9,4,183
-7,7,117~7,9,117
-3,2,63~4,2,63
-8,4,139~8,6,139
-4,7,11~4,7,11
-2,4,202~4,4,202
-3,7,241~4,7,241
-5,5,120~5,7,120
-0,1,237~1,1,237
-1,0,127~5,0,127
-7,4,292~9,4,292
-1,7,37~1,7,40
-7,0,177~7,2,177
-6,7,171~8,7,171
-1,3,218~1,6,218
-0,7,102~0,9,102
-3,6,249~4,6,249
-8,5,136~8,8,136
-4,2,45~7,2,45
-3,5,165~5,5,165
-7,7,241~8,7,241
-0,4,104~0,6,104
-7,5,51~7,7,51
-2,2,67~4,2,67
-6,1,191~6,3,191
-5,3,228~5,5,228
-4,5,209~4,7,209
-1,6,219~4,6,219
-2,0,171~2,2,171
-6,5,116~8,5,116
-6,1,288~6,3,288
-2,1,218~6,1,218
-7,8,169~9,8,169
-7,8,106~8,8,106
-2,0,250~2,2,250
-2,7,107~2,9,107
-9,8,181~9,9,181
-2,7,151~2,9,151
-3,3,86~5,3,86
-3,4,115~4,4,115
-0,7,146~2,7,146
-9,2,84~9,2,86
-9,3,5~9,4,5
-0,3,194~1,3,194
-1,2,274~1,3,274
-1,5,132~4,5,132
-6,5,294~6,5,297
-6,2,25~8,2,25
-3,7,52~3,9,52
-3,8,35~5,8,35
-1,9,3~1,9,4
-6,6,219~9,6,219
-1,3,118~3,3,118
-7,7,207~7,9,207
-9,7,262~9,8,262
-5,2,79~5,4,79
-2,0,220~2,1,220
-9,1,259~9,2,259
-2,1,128~4,1,128
-7,8,213~7,9,213
-2,6,128~2,6,129
-4,4,106~8,4,106
-0,5,78~3,5,78
-4,4,201~7,4,201
-4,7,62~4,9,62
-5,8,82~5,9,82
-0,5,83~2,5,83
-3,2,225~3,4,225
-7,7,140~8,7,140
-5,2,15~5,4,15
-5,7,161~7,7,161
-8,7,133~8,8,133
-1,1,230~4,1,230
-7,1,8~9,1,8
-1,4,156~3,4,156
-2,1,174~2,1,176
-8,7,257~8,7,259
-0,9,247~2,9,247
-1,3,147~1,3,149
-6,0,206~8,0,206
-6,1,151~8,1,151
-8,6,293~8,7,293
-5,1,211~5,3,211
-1,4,222~4,4,222
-1,5,23~1,7,23
-3,4,47~3,5,47
-1,6,85~1,8,85
-0,0,80~0,2,80
-7,3,215~7,3,218
-0,3,135~0,6,135
-5,7,177~6,7,177
-3,2,221~3,4,221
-9,7,63~9,8,63
-6,7,197~8,7,197
-0,2,277~2,2,277
-2,8,211~4,8,211
-1,7,132~4,7,132
-9,6,178~9,8,178
-5,0,222~5,3,222
-0,1,14~0,3,14
-6,4,256~6,5,256
-2,7,65~5,7,65
-3,3,170~3,4,170
-0,2,233~0,5,233
-4,4,12~7,4,12
-6,5,59~6,5,61
-5,1,237~5,2,237
-4,6,48~4,8,48
-1,5,135~1,5,136
-6,0,47~6,1,47
-1,6,84~3,6,84
-1,5,179~1,7,179
-4,7,138~4,9,138
-2,1,28~5,1,28
-4,1,155~4,2,155
-1,1,64~1,1,66
-4,4,32~6,4,32
-0,5,146~1,5,146
-4,6,71~4,8,71
-9,2,244~9,4,244
-5,2,212~5,3,212
-6,3,156~7,3,156
-9,6,10~9,8,10
-0,5,153~1,5,153
-1,7,102~1,7,104
-8,1,272~9,1,272
-4,7,123~7,7,123
-2,9,29~4,9,29
-0,5,133~3,5,133
-4,1,172~4,4,172
-7,7,90~7,8,90
-6,9,123~8,9,123
-6,2,233~6,2,234
-3,1,30~3,1,31
-1,4,280~1,6,280
-5,0,51~7,0,51
-7,8,83~7,8,85
-9,4,83~9,6,83
-5,5,104~7,5,104
-0,3,17~2,3,17
-3,6,47~3,6,48
-7,0,121~7,2,121
-6,5,11~8,5,11
-1,2,279~1,2,282
-2,6,162~3,6,162
-5,3,254~5,6,254
-5,1,95~6,1,95
-8,1,28~9,1,28
-3,3,120~3,6,120
-7,2,244~8,2,244
-0,3,166~3,3,166
-2,5,190~4,5,190
-9,7,101~9,8,101
-4,7,238~4,9,238
-2,2,260~4,2,260
-0,7,274~2,7,274
-0,1,279~0,4,279
-8,4,123~8,5,123
-9,2,248~9,4,248
-9,4,2~9,4,3
-2,6,115~5,6,115
-2,5,180~4,5,180
-4,5,221~4,7,221
-4,0,168~7,0,168
-4,7,53~7,7,53
-2,2,253~2,4,253
-3,5,163~5,5,163
-5,1,251~5,3,251
-9,7,232~9,7,233
-6,1,258~6,3,258
-9,7,252~9,9,252
-9,3,212~9,6,212
-7,5,94~9,5,94
-7,5,268~8,5,268
-5,3,28~8,3,28
-5,6,233~7,6,233
-0,1,83~0,3,83
-3,0,100~5,0,100
-0,9,99~3,9,99
-9,7,24~9,9,24
-9,3,34~9,3,36
-5,5,300~5,7,300
-0,0,236~0,3,236
-0,5,2~2,5,2
-5,4,237~5,6,237
-8,1,87~8,3,87
-6,6,289~8,6,289
-8,7,256~9,7,256
-1,9,1~3,9,1
-5,5,48~8,5,48
-9,5,42~9,7,42
-6,3,46~6,5,46
-3,3,167~3,5,167
-3,0,132~3,2,132
-4,6,9~4,9,9
-8,5,266~9,5,266
-5,3,62~5,6,62
-2,1,81~2,3,81
-7,4,86~7,6,86
-3,1,84~3,3,84
-5,5,115~7,5,115
-1,6,226~1,7,226
-6,5,187~6,8,187
-9,6,99~9,7,99
-7,2,116~7,3,116
-2,4,5~2,6,5
-2,2,212~2,5,212
-2,1,229~4,1,229
-7,9,143~9,9,143
-5,1,303~6,1,303
-0,0,130~1,0,130
-3,0,162~3,1,162
-5,0,200~5,2,200
-5,6,200~5,8,200
-8,5,64~8,8,64
-7,7,217~7,7,220
-6,7,163~9,7,163
-4,7,274~7,7,274
-2,8,200~3,8,200
-5,6,21~8,6,21
-3,4,163~5,4,163
-3,4,109~3,7,109
-9,8,175~9,8,175
-5,1,119~7,1,119
-2,9,195~4,9,195
-8,3,125~8,3,126
-5,4,198~5,7,198
-0,0,87~3,0,87
-6,4,9~6,5,9
-9,3,68~9,5,68
-5,1,239~5,3,239
-7,3,177~7,6,177
-4,8,20~5,8,20
-4,9,30~7,9,30
-3,4,184~6,4,184
-8,2,222~8,2,224
-0,4,170~0,6,170
-6,4,98~6,4,100
-0,8,270~2,8,270
-5,7,195~5,9,195
-3,9,273~3,9,273
-3,5,255~6,5,255
-4,0,10~5,0,10
-2,1,113~5,1,113
-0,5,269~0,6,269
-7,6,40~9,6,40
-4,4,301~4,7,301
-4,3,155~4,5,155
-4,3,110~4,5,110
-1,3,90~2,3,90
-7,4,87~7,6,87
-7,7,177~9,7,177
-5,0,84~8,0,84
-9,6,214~9,8,214
-4,6,18~5,6,18
-6,2,97~8,2,97
-4,4,22~4,7,22
-2,7,98~2,9,98
-5,8,26~6,8,26
-5,8,81~7,8,81
-6,7,262~6,7,263
-4,0,262~4,3,262
-6,6,245~7,6,245
-5,1,19~5,4,19
-6,0,211~6,2,211
-6,3,203~6,5,203
-1,3,81~1,5,81
-7,8,113~9,8,113
-3,4,7~3,4,8
-3,7,176~4,7,176
-2,9,214~2,9,217
-3,2,141~3,5,141
-7,5,3~7,7,3
-6,3,144~6,6,144
-8,3,121~8,5,121
-5,5,76~8,5,76
-3,2,126~6,2,126
-7,5,148~7,6,148
-2,8,110~4,8,110
-9,3,121~9,5,121
-6,7,241~6,9,241
-9,1,27~9,3,27
-5,5,207~5,5,209
-7,1,211~7,4,211
-9,5,263~9,7,263
-4,1,243~4,3,243
-0,6,80~0,8,80
-0,6,172~0,6,174
-0,2,230~0,5,230
-4,2,157~4,2,159
-5,1,214~5,2,214
-0,3,220~2,3,220
-9,1,219~9,1,221
-0,6,239~2,6,239
-1,8,7~1,8,8
-5,2,232~7,2,232
-0,8,32~1,8,32
-6,1,77~6,3,77
-7,6,56~7,8,56
-5,5,174~5,7,174
-6,7,205~6,9,205
-2,7,201~5,7,201
-5,9,83~5,9,84
-7,5,101~7,7,101
-4,3,173~4,6,173
-0,6,106~0,8,106
-5,2,230~7,2,230
-2,4,136~2,5,136
-2,2,70~2,2,73
-7,5,107~7,7,107
-4,0,200~4,2,200
-8,3,239~8,5,239
-1,8,155~4,8,155
-2,9,65~5,9,65
-3,4,116~4,4,116
-6,2,228~8,2,228
-1,2,20~1,4,20
-5,1,260~8,1,260
-2,6,52~3,6,52
-3,7,106~5,7,106
-0,2,269~0,4,269
-5,9,24~6,9,24
-0,9,208~3,9,208
-8,2,225~8,5,225
-1,7,184~1,9,184
-6,2,9~6,3,9
-0,6,53~0,8,53
-6,1,29~6,3,29
-1,8,139~2,8,139
-8,6,180~8,8,180
-6,3,17~7,3,17
-4,5,230~4,7,230
-6,1,252~6,3,252
-6,2,17~7,2,17
-0,4,150~0,6,150
-5,5,225~5,8,225
-4,4,292~5,4,292
-6,8,168~8,8,168
-4,7,29~6,7,29
-5,4,169~8,4,169
-4,0,224~6,0,224
-1,0,36~3,0,36
-7,8,15~9,8,15
-4,8,202~4,9,202
-9,1,81~9,3,81
-7,1,150~7,3,150
-5,6,212~5,8,212
-1,9,130~3,9,130
-2,1,271~2,1,274
-0,2,144~2,2,144
-3,0,124~3,2,124
-5,6,258~5,7,258
-4,1,71~4,3,71
-3,7,111~5,7,111
-9,4,44~9,7,44
-7,1,288~7,3,288
-5,3,127~5,5,127
-5,3,285~7,3,285
-3,6,293~5,6,293
-5,5,140~7,5,140
-3,2,296~4,2,296
-0,0,92~0,1,92
-3,3,121~3,3,124
-7,1,214~7,4,214
-4,0,88~4,1,88
-4,7,178~4,9,178
-7,8,114~7,9,114
-6,3,289~9,3,289
-0,3,222~0,6,222
-4,1,1~6,1,1
-0,0,148~0,2,148
-3,0,251~3,2,251
-4,8,93~4,9,93
-7,0,126~7,2,126
-0,2,197~0,3,197
-1,2,23~1,2,25
-4,5,168~6,5,168
-2,1,127~3,1,127
-0,6,124~2,6,124
-1,3,66~1,3,69
-6,9,115~8,9,115
-3,2,190~3,2,191
-4,3,124~4,5,124
-4,0,167~4,1,167
-4,3,277~4,6,277
-3,3,287~5,3,287
-6,0,29~8,0,29
-6,1,26~9,1,26
-8,7,5~8,9,5
-2,0,2~2,0,5
-0,3,176~0,5,176
-7,6,199~7,6,201
-8,2,39~8,2,42
-4,0,152~4,2,152
-7,1,129~9,1,129
-7,9,15~9,9,15
-3,1,85~5,1,85
-2,2,242~5,2,242
-2,0,43~4,0,43
-5,3,219~5,4,219
-2,5,236~2,5,237
-6,4,124~7,4,124
-5,8,53~6,8,53
-0,2,147~0,4,147
-6,4,136~7,4,136
-5,6,64~5,6,64
-7,9,256~9,9,256
-5,3,60~8,3,60
-1,8,262~3,8,262
-5,1,208~7,1,208
-3,6,46~5,6,46
-8,1,180~8,4,180
-2,2,185~3,2,185
-6,9,38~6,9,40
-3,1,265~3,3,265
-3,3,125~3,6,125
-2,2,248~5,2,248
-8,0,263~9,0,263
-2,2,255~2,2,256
-1,7,87~1,9,87
-5,1,279~5,1,281
-5,6,194~5,9,194
-0,5,177~3,5,177
-8,1,178~8,2,178
-5,3,261~8,3,261
-9,1,245~9,2,245
-5,1,93~5,3,93
-3,7,251~5,7,251
-4,4,65~6,4,65
-6,7,232~6,9,232
-9,1,5~9,1,5
-2,9,271~4,9,271
-5,0,223~7,0,223
-8,6,132~8,7,132
-5,6,264~5,8,264
-5,3,130~5,3,132
-6,7,70~6,7,72
-7,4,171~7,6,171
-4,2,46~6,2,46
-0,2,280~0,4,280
-3,0,45~3,1,45
-4,8,33~5,8,33
-6,3,151~7,3,151
-5,8,38~5,8,40
-4,5,299~6,5,299
-3,1,1~3,1,3
-1,3,221~2,3,221
-3,1,96~4,1,96
-1,6,181~1,7,181
-5,4,196~5,6,196
-9,0,3~9,0,4
-6,5,91~6,8,91
-4,0,162~4,3,162
-5,2,163~6,2,163
-4,4,306~5,4,306
-5,3,4~5,5,4
-4,7,243~4,9,243
-7,4,102~8,4,102
-7,2,133~7,4,133
-4,7,38~6,7,38
-4,8,32~6,8,32
-1,2,8~1,3,8
-5,8,209~6,8,209
-6,7,237~6,9,237
-3,7,261~6,7,261
-2,4,25~2,6,25
-8,7,107~8,9,107
-2,1,159~5,1,159
-5,4,37~5,7,37
-9,7,250~9,8,250
-5,1,24~5,3,24
-2,7,196~2,9,196
-3,3,205~3,3,207
-3,6,164~4,6,164
-0,0,181~3,0,181
-0,1,129~0,1,132
-5,5,57~8,5,57
-8,5,187~8,6,187
-3,0,129~6,0,129
-3,0,33~3,2,33
-3,2,195~3,4,195
-0,5,138~0,6,138
-6,7,272~8,7,272
-3,2,267~5,2,267
-3,6,68~3,8,68
-1,8,160~3,8,160
-7,3,130~7,4,130
-0,5,234~0,8,234
-1,5,233~4,5,233
-4,5,125~4,6,125
-0,1,88~1,1,88
-8,1,185~8,3,185
-3,1,224~3,4,224
-2,2,6~2,4,6
-2,9,132~3,9,132
-5,0,99~8,0,99
-7,7,252~7,8,252
-8,6,104~8,8,104
-2,9,221~2,9,221
-5,3,178~5,6,178
-1,3,117~3,3,117
-3,2,17~5,2,17
-1,3,2~1,3,5
-1,9,53~3,9,53
-1,2,259~3,2,259
-4,5,303~4,9,303
-5,2,205~5,6,205
-9,9,79~9,9,81
-4,3,203~4,5,203
-0,7,268~0,8,268
-8,5,109~8,7,109
-3,6,86~5,6,86
-3,5,89~3,8,89
-2,6,1~2,6,3
-0,1,123~2,1,123
-4,1,219~4,1,219
-0,4,85~0,5,85
-9,5,247~9,7,247
-1,1,75~1,3,75
-5,8,278~7,8,278
-1,2,64~1,3,64
-6,7,194~6,7,194
-7,0,86~9,0,86
-1,3,72~3,3,72
-8,4,167~8,6,167
-7,8,236~9,8,236
-1,1,207~2,1,207
-8,6,105~8,9,105
-5,5,81~5,6,81
-0,4,11~2,4,11
-8,0,27~8,2,27
-0,7,83~0,7,86
-5,2,112~5,4,112
-1,4,227~1,6,227
-1,2,58~3,2,58
-3,6,222~3,8,222
-1,1,86~3,1,86
-5,3,23~5,6,23
-8,2,176~8,4,176
-8,5,37~8,7,37
-2,2,66~2,5,66
-5,2,32~6,2,32
-0,2,60~3,2,60
-0,9,211~2,9,211
-8,1,24~8,3,24
-4,6,222~6,6,222
-8,4,13~8,6,13
-6,1,256~9,1,256
-6,4,1~6,4,3
-8,1,242~8,3,242
-0,5,144~0,8,144
-8,4,175~8,5,175
-6,7,239~7,7,239
-3,4,255~5,4,255
-4,1,226~4,3,226
-7,1,107~7,2,107
-1,7,99~1,8,99
-4,2,18~4,3,18
-1,1,27~1,3,27
-0,2,173~0,5,173
-3,2,78~4,2,78
-4,3,133~4,6,133
-1,6,208~2,6,208
-6,1,112~7,1,112
-0,8,4~3,8,4
-9,2,6~9,4,6
-3,2,168~4,2,168
-5,6,207~5,7,207
-3,8,257~5,8,257
-4,8,31~6,8,31
-0,4,49~0,5,49
-3,6,193~3,9,193
-3,1,157~3,3,157
-6,3,138~6,5,138
-4,4,205~4,4,205
-5,6,236~8,6,236
-6,3,134~6,5,134
-0,7,254~3,7,254
-0,2,268~3,2,268
-8,5,241~8,5,243
-6,5,106~6,5,109
-2,2,170~4,2,170
-3,9,203~3,9,205
-9,6,68~9,9,68
-4,3,251~4,5,251
-1,5,112~3,5,112
-5,4,125~5,6,125
-6,1,131~7,1,131
-0,6,224~2,6,224
-2,3,209~4,3,209
-1,3,111~3,3,111
-2,7,265~3,7,265
-4,5,108~5,5,108
-0,1,62~2,1,62
-6,7,190~8,7,190
-7,1,104~7,3,104
-5,5,176~7,5,176
-6,8,3~6,9,3
-6,8,234~8,8,234
-6,9,8~6,9,10
-0,8,157~3,8,157
-4,8,254~6,8,254
-7,5,182~7,5,185
-5,8,23~5,9,23
-3,6,73~4,6,73
-6,3,209~6,3,209
-5,0,97~5,1,97
-1,5,242~3,5,242
-5,1,215~5,2,215
-9,5,186~9,7,186
-7,9,21~9,9,21
-3,6,70~3,8,70
-3,4,37~4,4,37
-6,6,129~9,6,129
-3,0,165~5,0,165
-5,9,206~8,9,206
-5,1,297~5,4,297
-2,4,187~2,5,187
-2,9,100~4,9,100
-7,2,215~9,2,215
-5,8,127~7,8,127
-1,6,174~4,6,174
-1,7,134~1,8,134
-1,4,104~1,4,106
-4,7,269~6,7,269
-6,0,14~6,3,14
-1,1,63~1,2,63
-2,4,57~4,4,57
-4,1,147~4,4,147
-5,6,66~6,6,66
-7,3,179~7,5,179
-3,0,83~4,0,83
-7,2,52~8,2,52
-6,1,250~8,1,250
-3,6,232~3,6,233
-6,1,6~7,1,6
-0,1,11~3,1,11
-8,4,251~9,4,251
-2,2,79~2,5,79
-4,8,55~5,8,55
-1,4,122~1,4,122
-4,7,20~6,7,20
-5,4,53~7,4,53
-0,6,102~2,6,102
-4,4,44~7,4,44
-0,1,90~0,2,90
-5,3,101~8,3,101
-4,2,292~4,2,295
-3,5,230~3,7,230
-2,7,260~2,8,260
-5,1,266~5,4,266
-3,4,97~6,4,97
-4,2,143~4,4,143
-1,4,277~1,7,277
-7,2,129~7,4,129
-1,1,126~2,1,126
-6,1,290~6,1,292
-7,2,218~7,2,220
-9,0,89~9,2,89
-9,4,118~9,6,118
-2,1,122~5,1,122
-0,8,113~3,8,113
-7,7,245~9,7,245
-7,4,14~7,6,14
-1,1,240~1,1,240
-5,1,158~5,2,158
-0,2,26~1,2,26
-0,1,124~0,4,124
-0,1,278~0,3,278
-3,7,202~3,7,205
-5,2,165~5,3,165
-0,6,50~3,6,50
-5,1,45~5,1,48
-2,4,257~3,4,257
-6,4,139~6,4,142
-7,3,99~7,5,99
-8,5,208~8,6,208
-1,3,144~4,3,144
-6,0,213~8,0,213
-4,1,255~6,1,255
-0,4,62~3,4,62
-4,2,74~6,2,74
-5,7,218~5,9,218
-1,0,251~2,0,251
-4,5,89~4,7,89
-5,6,40~6,6,40
-7,3,13~7,6,13
-2,4,3~3,4,3
-1,4,70~1,5,70
-2,9,219~2,9,220
-0,7,264~0,9,264
-4,1,149~7,1,149
-2,9,248~4,9,248
-8,7,295~8,7,297
-6,4,253~9,4,253
-1,1,134~3,1,134
-3,2,85~3,4,85
-7,2,2~7,4,2
-9,5,192~9,5,194
-6,3,4~6,6,4
-0,6,8~0,6,10
-4,0,197~6,0,197
-0,3,257~2,3,257
-4,0,181~4,2,181
-9,9,182~9,9,184
-6,6,69~6,6,71
-2,7,207~4,7,207
-7,1,2~9,1,2
-6,4,236~9,4,236
-1,2,103~1,5,103
-6,8,206~8,8,206
-2,4,8~2,5,8
-6,3,205~6,3,208
-1,3,188~3,3,188
-3,5,81~3,7,81
-7,9,121~9,9,121
-1,4,160~1,4,161
-3,8,252~5,8,252
-6,0,194~6,3,194
-2,4,231~4,4,231
-9,5,65~9,7,65
-5,2,218~5,5,218
-3,5,17~5,5,17
-5,4,269~5,6,269
-4,2,216~4,2,218
-6,0,12~6,3,12
-6,6,147~7,6,147
-7,0,88~7,0,91
-6,6,195~6,7,195
-4,8,143~4,9,143
-8,8,66~9,8,66
-6,8,172~8,8,172
-2,7,6~4,7,6
-3,7,83~3,7,85
-2,5,291~6,5,291
-4,9,128~5,9,128
-7,3,237~7,5,237
-1,3,89~5,3,89
-5,2,82~7,2,82
-6,0,123~8,0,123
-8,2,181~9,2,181
-5,8,134~8,8,134
-4,9,26~6,9,26
-7,8,187~8,8,187
-6,1,58~8,1,58
-1,0,89~2,0,89
-0,8,147~2,8,147
-8,3,22~8,6,22
-0,4,48~3,4,48
-2,5,143~3,5,143
-4,0,37~4,2,37
-6,4,120~6,7,120
-4,8,271~7,8,271
-3,4,304~3,6,304
-4,4,72~5,4,72
-6,4,105~7,4,105
-7,0,243~7,2,243
-8,2,172~8,4,172
-7,0,124~9,0,124
-4,7,233~5,7,233
-1,1,77~1,1,79
-4,8,34~6,8,34
-8,8,208~8,9,208
-5,7,126~5,8,126
-0,7,150~0,8,150
-7,7,37~7,7,40
-5,1,3~7,1,3
-2,6,164~2,7,164
-3,0,8~3,2,8
-7,8,211~7,9,211
-8,9,253~9,9,253
-8,6,291~8,8,291
-6,1,78~9,1,78
-5,7,162~5,9,162
-6,3,270~6,5,270
-3,2,218~3,3,218
-7,4,139~7,6,139
-4,4,129~4,5,129
-4,7,69~7,7,69
-4,8,141~4,9,141
-7,7,138~9,7,138
-6,4,127~6,6,127
-8,7,110~8,9,110
-5,8,228~8,8,228
-4,6,118~4,7,118
-9,7,70~9,9,70
-0,8,237~0,9,237
-6,7,168~9,7,168
-2,2,175~5,2,175
-7,7,15~9,7,15
-3,4,5~3,7,5
-6,3,123~8,3,123
-5,1,111~7,1,111
-6,3,6~6,5,6
-1,3,152~4,3,152
-3,4,19~3,6,19
-2,7,165~2,8,165
-0,9,105~2,9,105
-4,7,59~6,7,59
-1,3,190~1,5,190
-3,6,20~3,7,20
-8,5,210~9,5,210
-6,3,55~6,6,55
-8,1,220~8,3,220
-4,9,66~4,9,66
-4,7,203~5,7,203
-1,7,149~2,7,149
-6,7,199~6,8,199
-7,2,46~9,2,46
-5,9,208~6,9,208
-0,3,114~3,3,114
-7,6,132~7,8,132
-3,3,59~6,3,59
-2,3,286~5,3,286
-5,0,26~5,3,26
-9,6,1~9,6,2
-4,5,131~4,8,131
-4,3,94~4,3,97
-3,1,252~3,1,253
-9,3,184~9,7,184
-8,6,120~8,7,120
-0,4,240~0,6,240
-1,1,224~1,3,224
-8,9,3~9,9,3
-7,4,36~7,4,39
-4,5,14~4,7,14
-8,5,65~8,5,66
-4,8,247~5,8,247
-7,0,153~7,3,153
-0,0,127~0,2,127
-1,2,106~4,2,106
-5,1,182~8,1,182
-4,0,39~6,0,39
-4,2,34~4,4,34
-0,4,226~0,5,226
-5,4,275~5,5,275
-7,8,60~7,9,60
-7,1,42~7,4,42
-3,2,56~3,4,56
-5,4,215~7,4,215
-6,4,131~6,6,131
-4,5,127~4,8,127
-1,8,137~1,8,138
-9,7,231~9,8,231
-7,6,198~7,8,198
-3,4,114~5,4,114
-5,2,139~8,2,139
-3,1,242~6,1,242
-0,3,88~0,5,88
-0,7,276~0,9,276
-6,7,191~7,7,191
-0,8,199~2,8,199
-5,8,4~6,8,4
-7,6,204~7,8,204
-0,7,149~0,9,149
-1,7,35~1,9,35
-7,4,71~7,7,71
-7,7,66~8,7,66
-3,5,158~6,5,158
-3,2,182~5,2,182
-2,6,104~2,7,104
-0,4,108~0,6,108
-8,3,264~8,5,264
-4,2,2~4,4,2
-4,1,223~5,1,223
-7,0,117~7,2,117
-6,7,202~8,7,202
-7,8,174~9,8,174
-1,9,131~3,9,131
-6,6,165~6,8,165
-4,7,204~5,7,204
-3,6,256~6,6,256
-1,7,126~2,7,126
-8,0,136~9,0,136
-0,6,181~0,9,181
-4,1,301~5,1,301
-5,5,56~5,7,56
-7,1,278~7,3,278
-2,8,153~4,8,153
-8,7,182~8,8,182
-4,0,263~6,0,263
-0,6,90~0,7,90
-3,0,109~3,3,109
-4,2,70~4,5,70
-5,5,85~5,5,88
-4,0,42~6,0,42
-0,3,61~2,3,61
-2,1,59~2,3,59
-6,7,174~9,7,174
-6,7,7~8,7,7
-8,2,1~8,4,1
-4,0,139~8,0,139
-0,3,228~1,3,228
-5,8,249~7,8,249
-6,4,230~6,7,230
-2,0,84~2,2,84
-9,0,131~9,2,131
-8,5,164~8,7,164
-9,7,254~9,7,254
-3,6,16~4,6,16
-5,9,125~8,9,125
-4,7,173~7,7,173
-2,8,108~2,9,108
-8,4,214~8,5,214
-3,8,196~3,8,197
-0,4,90~0,4,90
-7,6,58~7,9,58
-1,4,159~1,7,159
-0,0,253~2,0,253
-6,6,90~9,6,90
-0,1,151~0,3,151
-0,1,64~0,2,64
-4,4,248~4,7,248
-5,6,288~8,6,288
-4,3,141~4,4,141
-3,2,5~3,2,6
-3,8,190~4,8,190
-9,2,115~9,5,115
-1,6,3~1,6,4
-8,4,49~8,7,49
-3,5,274~6,5,274
-2,8,53~3,8,53
-6,4,111~6,7,111
-7,3,82~7,5,82
-7,7,214~7,9,214
-3,3,49~6,3,49
-0,9,114~2,9,114
-3,3,65~5,3,65
-1,7,96~4,7,96
-6,6,103~8,6,103
-1,8,163~3,8,163
-6,8,185~8,8,185
-7,2,271~7,2,274
-2,4,59~4,4,59
-8,0,261~8,2,261
-5,1,163~8,1,163
-2,1,206~3,1,206
-6,5,83~7,5,83
-7,3,220~7,4,220
-0,8,2~2,8,2
-8,1,231~8,4,231
-6,3,286~6,6,286
-2,0,13~3,0,13
-4,1,267~7,1,267
-0,5,73~2,5,73
-3,6,201~5,6,201
-1,4,178~1,6,178
-6,0,294~6,2,294
-1,6,30~1,8,30
-7,4,35~7,5,35
-0,6,89~0,8,89
-1,2,146~1,2,148
-9,9,76~9,9,77
-3,3,45~3,7,45
-5,3,74~5,5,74
-9,2,30~9,4,30
-3,2,228~3,3,228
-6,1,56~6,3,56
-1,7,229~1,7,231
-2,1,38~4,1,38
-2,7,257~4,7,257
-1,8,101~3,8,101
-7,5,105~9,5,105
-1,6,222~2,6,222
-5,3,179~5,6,179
-2,8,132~4,8,132
-6,1,80~6,4,80
-7,2,72~7,4,72
-7,3,141~7,4,141
-0,5,228~3,5,228
-6,6,5~6,9,5
-7,2,135~9,2,135
-7,1,108~7,2,108
-5,4,295~8,4,295
-0,4,178~0,6,178
-8,6,184~8,8,184
-6,9,33~6,9,35
-4,8,133~4,8,135
-4,0,169~7,0,169
-7,9,118~8,9,118
-6,5,32~8,5,32
-3,6,255~5,6,255
-8,2,213~8,5,213
-8,2,49~9,2,49
-0,5,27~2,5,27
-1,6,236~3,6,236
-5,4,189~8,4,189
-1,1,278~3,1,278
-4,1,161~6,1,161
-2,5,295~2,5,297
-2,4,53~4,4,53
-3,6,204~5,6,204
-1,6,156~1,9,156
-8,9,259~9,9,259
-2,0,182~2,0,185
-3,6,43~5,6,43
-3,2,264~5,2,264
-1,9,202~3,9,202
-3,5,49~3,7,49
-6,4,31~6,6,31
-1,0,186~3,0,186
-7,6,35~7,8,35
-6,2,188~6,5,188
-0,5,22~3,5,22
-6,4,113~6,6,113
-3,8,50~5,8,50
-2,3,121~2,5,121
-2,1,162~2,3,162
-0,3,87~0,5,87
-0,3,259~2,3,259
-1,5,29~1,5,30
-4,5,117~5,5,117
-3,4,234~3,5,234
-4,8,208~7,8,208
-0,3,193~3,3,193
-9,3,130~9,6,130
-4,0,80~4,3,80
-7,9,18~7,9,19
-5,2,203~5,4,203
-3,6,92~5,6,92
-7,2,113~9,2,113
-2,5,11~2,5,12
-6,2,173~9,2,173
-5,6,35~5,7,35
-2,8,244~4,8,244
-2,3,96~2,5,96
-0,5,279~0,7,279
-3,4,187~3,4,188
-6,6,106~6,9,106
-7,6,117~9,6,117
-5,0,101~8,0,101
-3,0,104~5,0,104
-1,5,77~4,5,77
-4,4,121~7,4,121
-8,5,188~9,5,188
-3,6,258~3,7,258
-5,4,290~5,6,290
-2,6,205~4,6,205
-3,2,98~3,4,98
-7,2,96~7,6,96
-7,6,6~8,6,6
-4,6,227~6,6,227
-0,2,143~3,2,143
-1,7,200~1,9,200
-2,2,94~4,2,94
-6,8,236~6,9,236
-9,2,1~9,3,1
-5,1,15~8,1,15
-0,2,79~0,5,79
-2,1,269~5,1,269
-2,8,18~5,8,18
-2,3,256~2,5,256
-6,4,289~8,4,289
-5,1,210~8,1,210
-5,7,280~7,7,280
-9,7,141~9,9,141
-4,5,231~7,5,231
-4,1,291~4,3,291
-6,8,273~8,8,273
-3,9,127~5,9,127
-2,3,3~5,3,3
-1,4,138~4,4,138
-0,1,226~0,3,226
-7,6,1~7,8,1
-7,4,15~7,6,15
-6,8,8~9,8,8
-4,4,104~7,4,104
-5,1,98~5,1,99
-3,2,288~3,4,288
-6,6,62~6,7,62
-6,8,173~6,9,173
-1,2,172~3,2,172
-2,8,276~5,8,276
-8,2,243~8,4,243
-0,3,267~3,3,267
-9,5,279~9,8,279
-2,4,305~2,4,306
-2,9,200~4,9,200
-2,5,294~5,5,294
-6,4,241~9,4,241
-3,8,189~6,8,189
-2,6,86~2,6,89
-5,2,77~5,5,77
-1,7,78~1,8,78
-9,3,131~9,4,131
-6,0,92~8,0,92
-7,4,297~8,4,297
-4,9,11~7,9,11
-3,4,75~3,6,75
-7,0,290~7,2,290
-3,2,188~3,2,188
-4,2,279~4,4,279
-3,3,154~3,4,154
-2,5,23~4,5,23
-1,6,281~1,8,281
-1,9,101~1,9,102
-0,4,267~0,7,267
-0,7,77~2,7,77
-6,2,58~6,2,60
-4,1,44~7,1,44
-4,8,51~4,8,53
-8,5,97~8,7,97
-3,1,165~3,4,165
-0,6,141~1,6,141
-1,5,239~2,5,239
-9,9,72~9,9,73
-1,2,271~2,2,271
-8,3,223~8,5,223
-6,0,114~6,2,114
-1,5,101~1,7,101
-3,4,162~5,4,162
-6,2,291~9,2,291
-2,1,187~2,3,187
-1,5,75~1,7,75
-2,4,303~5,4,303
-0,6,227~0,8,227
-9,3,96~9,7,96
-6,0,134~6,2,134
-2,3,153~2,5,153
-1,9,135~3,9,135
-9,9,186~9,9,187
-5,6,114~8,6,114
-5,4,185~5,4,187
-9,2,217~9,2,220
-2,7,233~3,7,233
-4,1,246~4,2,246
-2,1,277~5,1,277
-5,3,267~8,3,267
diff --git a/22/src/main.rs b/22/src/main.rs
index 13385bd..cdd6156 100644
--- a/22/src/main.rs
+++ b/22/src/main.rs
@@ -1,7 +1,8 @@
 use itertools::Itertools;
 use ndarray::prelude::*;
-use std::borrow::BorrowMut;
-use std::collections::{BinaryHeap, HashMap, VecDeque};
+use petgraph::prelude::*;
+use petgraph::visit::{IntoNodeReferences, Walker};
+use std::collections::BinaryHeap;
 use std::fmt::{Display, Write};
 use std::fs::File;
 use std::io::{BufRead, BufReader, Lines};
@@ -67,16 +68,6 @@ impl std::fmt::Debug for BrickBlock {
 }
 
 impl BrickBlock {
-    fn map_remove(&self, mut map: BlockMap) -> BlockMap {
-        // loop over the (inclusive) bounding coordinates and remove them all from the map
-        map.slice_mut(s![
-            std::cmp::min(self.c1.x, self.c2.x)..std::cmp::max(self.c1.x, self.c2.x) + 1,
-            std::cmp::min(self.c1.y, self.c2.y)..std::cmp::max(self.c1.y, self.c2.y) + 1,
-            std::cmp::min(self.c1.z, self.c2.z)..std::cmp::max(self.c1.z, self.c2.z) + 1
-        ])
-        .fill(None);
-        map
-    }
     fn map_into(&self, mut map: BlockMap) -> BlockMap {
         // loop over the (inclusive) bounding coordinates and add them all to the map
         map.slice_mut(s![
@@ -137,6 +128,7 @@ struct BlockPile {
     blocks: Vec<BrickBlock>,
     block_map: Array3<MapTile>,
     bounds: (usize, usize, usize),
+    graph: Graph<BrickBlock, (), Directed, usize>,
 }
 
 impl BlockPile {
@@ -172,31 +164,26 @@ impl BlockPile {
             block.top_z_plane() + 1..std::cmp::min(block.top_z_plane() + 2, self.bounds.2)
         ]);
 
-        directly_above.iter().filter_map(|v| v.clone()).dedup().collect()
+        directly_above.iter().filter_map(|v| v.clone()).unique().collect()
     }
     fn supported_by(&self, block: &BrickBlock) -> usize {
-        println!("{:?} is supported by:", block);
         let z_plane = std::cmp::min(block.c1.z, block.c2.z);
-        println!(" z plane: {}", z_plane);
         // get the slice of tiles below us
         let directly_below = self.block_map.slice(s![
             block.bottom_x_plane()..block.top_x_plane() + 1,
             block.bottom_y_plane()..block.top_y_plane() + 1,
-            z_plane - 1..z_plane // don't include our own plane
+            z_plane - 1..z_plane // the layer below
         ]);
-        println!(
-            "  {} directly below {:?}",
-            directly_below.iter().filter_map(|v| v.clone()).dedup().count(),
-            block
-        );
-        directly_below.iter().filter_map(|v| v.clone()).dedup().count()
+        directly_below.iter().filter_map(|v| v.clone()).unique().count()
     }
     fn blocks_above_will_move_if_we_are_gone(&mut self, block: &BrickBlock) -> bool {
-        println!("checking directly above block {:?}", block);
         self.blocks_directly_above(&block)
             .iter()
             .map(|b| self.supported_by(b))
-            .any(|b| b == 1) // 0 can happen at the origin, and an empty iterator (falsy) will happen at the top
+            .any(|b| b == 1) // block we support will move if we are their only support
+    }
+    fn blocks_supported_by_at_all(&self, block: &BrickBlock) -> Vec<BrickBlock> {
+        self.blocks_directly_above(&block).iter().map(|b| b.clone()).collect()
     }
     /// Find the plane of the first block directly below us
     fn supporting_plane(&self, block: &BrickBlock) -> Option<usize> {
@@ -222,51 +209,38 @@ impl BlockPile {
     }
 
     fn drop_blocks(&mut self) {
+        // VecDeque doesn't sort and Vec isn't convenient for pushback and popfront, so eh... use a heap.
         let mut blocks_to_move = BinaryHeap::from(self.blocks.clone());
         while let Some(mut block) = blocks_to_move.pop() {
-            match self.supporting_plane(&block) {
-                Some(z) if z + 1 != block.bottom_z_plane() => {
-                    // we can move down to this position
-                    // set old position to None
-                    self.remove_block(&block);
-                    // set new positions
-                    let z_height = block.c1.z.abs_diff(block.c2.z);
-                    block.c1.z = z + 1;
-                    block.c2.z = z + 1 + z_height;
-                    self.add_block(&block);
-                    // queue the block again
-                    blocks_to_move.push(block);
-                }
-                None if block.bottom_z_plane() != 1 => {
-                    // we can move down to this position
-                    // set old position to None
-                    let z = 1;
-                    self.remove_block(&block);
-                    // set new positions
-                    let z_height = block.c1.z.abs_diff(block.c2.z);
-                    block.c1.z = z;
-                    block.c2.z = z + z_height;
-                    self.add_block(&block);
-                    // queue the block again
-                    blocks_to_move.push(block);
-                }
+            let z_move = match self.supporting_plane(&block) {
+                Some(z) if z + 1 != block.bottom_z_plane() => block.bottom_z_plane() - (z + 1),
+                None if block.bottom_z_plane() != 1 => block.bottom_z_plane() - 1,
                 _ => {
                     continue;
                 } // we are in position already with nothing below us
-            }
+            };
+            self.remove_block(&block);
+            block.c1.z -= z_move;
+            block.c2.z -= z_move;
+            self.add_block(&block);
+            blocks_to_move.push(block);
         }
     }
-    fn can_move(&self, block: &BrickBlock) -> bool {
-        match self.supporting_plane(&block) {
-            Some(z) if z + 1 != block.bottom_z_plane() => {
-                return true;
+    fn build_graph(&mut self) {
+        self.blocks.sort_by_key(|b| b.bottom_z_plane());
+        for b in 0..self.blocks.len() {
+            self.graph.add_node(self.blocks[b].clone());
+        }
+        for b in 0..self.blocks.len() {
+            let block = &self.blocks[b];
+            let depends_on_us = self.blocks_supported_by_at_all(block);
+            for dependent in depends_on_us {
+                self.graph.add_edge(
+                    b.into(),
+                    self.blocks.iter().position(|b| b == &dependent).unwrap().into(),
+                    (),
+                );
             }
-            None if block.bottom_z_plane() != 1 => {
-                return true;
-            }
-            _ => {
-                return false;
-            } // we are in position already with nothing below us
         }
     }
 }
@@ -277,6 +251,7 @@ impl<T: BufRead> From<Lines<T>> for BlockPile {
             blocks: lines.map(|line| BrickBlock::from(line.unwrap().as_str())).collect(),
             block_map: Array3::from_elem([0, 0, 0], None),
             bounds: (0, 0, 0),
+            graph: Graph::default(),
         };
 
         for block in &new.blocks {
@@ -338,25 +313,63 @@ fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
     println!("{}", pile);
 
     let blocks = pile.blocks.clone();
-    let mut must_keep: Vec<_> = blocks
-        .iter()
-        .filter(|b| pile.blocks_above_will_move_if_we_are_gone(*b))
-        .collect();
-    let mut removable: Vec<_> = blocks
+    let removable: Vec<_> = blocks
         .iter()
         .filter(|b| !pile.blocks_above_will_move_if_we_are_gone(*b))
         .collect();
-    removable.sort_by(|a, b| a.bottom_z_plane().cmp(&b.bottom_z_plane()));
-    must_keep.sort_by(|a, b| a.bottom_z_plane().cmp(&b.bottom_z_plane()));
-
-    println!("remove: {:?}", removable);
 
     removable.len() as u64
 }
 
 // PROBLEM 2 solution
 fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    0
+    let mut pile = BlockPile::from(input);
+    pile.drop_blocks();
+    pile.build_graph();
+
+    println!("{}", pile);
+    println!("block 0 {:?}", pile.blocks[0]);
+
+    let mut accum = 0;
+    let fixed_nodes = pile
+        .graph
+        .node_references()
+        .filter(|(_idx, b)| b.bottom_z_plane() == 1)
+        .map(|(idx, _b)| idx)
+        .collect_vec();
+    for node in pile.graph.node_indices() {
+        // remove links to node's neighbors
+        let dependents = pile.graph.neighbors(node).collect_vec();
+        let edges = pile.graph.edges(node).map(|v| v.id()).collect_vec();
+        for edge in edges {
+            pile.graph.remove_edge(edge);
+        }
+
+        // find how many nodes are reachable from z = 1 - these won't move
+        let safe_blocks = fixed_nodes
+            .iter()
+            .flat_map(|origin| {
+                Bfs::new(&pile.graph, *origin)
+                    .iter(&pile.graph)
+                    .map(|n| pile.graph[n].clone())
+            })
+            .unique()
+            .count();
+        // we are looking for the nodes that *will* disintegrate
+        println!(
+            "From {}, {} safe, {} disintegrate",
+            node.index(),
+            safe_blocks,
+            pile.graph.node_count() - safe_blocks
+        );
+        accum += pile.graph.node_count() - safe_blocks;
+        // put the graph back how it was
+        for neigh in dependents {
+            pile.graph.add_edge(node, neigh, ());
+        }
+    }
+    println!("blocks: {} nodes: {}", pile.blocks.len(), pile.graph.node_count());
+    accum as u64
 }
 
 #[cfg(test)]
@@ -381,6 +394,6 @@ mod tests {
     #[test]
     fn problem2_example() {
         let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem2(c.lines()), 0);
+        assert_eq!(problem2(c.lines()), 7);
     }
 }