Add solution for day 12

2022/day12/code.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+import sys
+
+
+def parse_graph(p):
+    graph = {}
+    start = None
+    end = None
+    a = []
+    for i in range(len(p)): # y dir
+        for j in range(len(p[i])): # x dir
+            if p[i][j] == 'S':
+                start = (j,i)
+                p[i][j] = 'a'
+            elif p[i][j] == 'E':
+                end = (j,i)
+                p[i][j] = 'z'
+            if p[i][j] == 'a': a.append((j,i))
+            graph[(j,i)] = []
+            for (x,y) in set([(max(0,j-1),i),(min(len(p[i])-1,j+1),i),(j,max(0,i-1)),(j,min(len(p)-1,i+1))]):
+                if (ord(p[y][x])-1)<=ord(p[i][j]): graph[(j,i)].append((x,y)) 
+    return graph, start, end, a
+
+
+def bfs(g,start,end):
+    Q = [start]
+    expl = [start]
+    parent = {}
+    parent[start] = None
+    while len(Q) > 0:
+        v = Q.pop(0)
+        if v == end: return parent
+        for w in g[v]:
+            if w not in expl:
+                expl.append(w)
+                parent[w] = v
+                Q.append(w)
+
+def path(parent, end):
+    length = 0
+    v = end
+    while parent[v] != None:
+        length = length + 1
+        v = parent[v]
+    return length
+
+
+if __name__ == '__main__':
+    points = [list(line.strip('\n')) for line in open(sys.argv[1])]
+
+    g, s, e, az = parse_graph(points)
+    par = bfs(g, s, e)
+    shortest = path(par,e)
+
+    # challenge 1
+    res1 = str(shortest)
+    print("challenge 1:" + "\n" +  res1 + "\n")
+
+    # challenge 2
+    for a in az:
+        par = bfs(g, a, e)
+        if par != None: s = path(par,e)
+        if s < shortest: shortest = s
+
+    res2 = str(shortest)
+    print("challenge 2:" + "\n" +  res2 + "\n")
+