Add solution for day 12

AoC2021/inputs/input12

@@ -0,0 +1,22 @@
+end-MY
+MY-xc
+ho-NF
+start-ho
+NF-xc
+NF-yf
+end-yf
+xc-TP
+MY-qo
+yf-TP
+dc-NF
+dc-xc
+start-dc
+yf-MY
+MY-ho
+EM-uh
+xc-yf
+ho-dc
+uh-NF
+yf-ho
+end-uh
+start-NF

AoC2021/inputs/test12A

@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end

AoC2021/inputs/test12B

@@ -0,0 +1,10 @@
+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc

AoC2021/inputs/test12C

@@ -0,0 +1,18 @@
+fs-end
+he-DX
+fs-he
+start-DX
+pj-DX
+end-zg
+zg-sl
+zg-pj
+pj-he
+RW-he
+fs-DX
+pj-RW
+zg-RW
+start-pj
+he-WI
+zg-he
+pj-fs
+start-RW