day 12, at last, some graph algorithm

d12/cmd.txt

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+pandoc -o fail.pdf -t pdf fail.md

d12/fail.md

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+
+
+I have only on patch of P
+
+![](P.png)
+
+\newpage
+
+So I have to choose this patch of Q
+
+![](Q.png)
+
+\newpage
+
+Then this patch of R
+
+![](R.png)
+
+\newpage
+
+then this patch of S
+
+![](S.png)
+
+\newpage
+
+But then, this patch of S is not connected to the patch of T
+
+![](T.png)
+
+I feel like i'm stucked :(
+
+But actually, [not](https://www.reddit.com/r/adventofcode/comments/zjqz5y/2022_day_12_is_my_input_invalid_or/)
+

d12/run.py

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+import sys
+import networkx as netx
+
+M = [ list(l) for l in sys.stdin.read().splitlines() ]
+H = len(M)
+W = len(M[0])
+START = tuple()
+END = tuple()
+G = netx.DiGraph()
+
+for x in range(H):
+    for y in range(W):
+        k = (x,y)
+        v = M[x][y]
+        if v == 'S':
+            START = k
+            v = 'a'
+        if v == 'E':
+            END = k
+            v = 'z'
+        v = ord(v)
+        for dx,dy in [(-1,0),(1,0),(0,-1),(0,1)]:
+            nx, ny = (x+dx, y+dy)
+            if nx>=0 and nx<H and ny>=0 and ny<W:
+                nk = (nx,ny)
+                nv = M[nx][ny]
+                if nv == 'S':
+                    nv = 'a'
+                if nv == 'E':
+                    nv = 'z'
+                nv = ord(nv)
+                dv = nv - v
+                if dv <=1:  # can go down !
+                    G.add_edge(k,nk)
+
+print(G)
+
+# part 1
+S = netx.shortest_path(G, START, END)
+print(len(S), "=>", len(S)-1)
+for (x,y) in S:
+    M[x][y] = "\033[30;43m"+M[x][y].upper()+"\033[0m"
+print("\n".join("".join(l) for l in M))
+
+# part 2
+R = []
+for x in range(H):
+    S = netx.shortest_path(G, (x,0), END)
+    R.append(len(S)-1)
+print(min(R))