Data commit

Task/Floyd-Warshall-algorithm/Python/floyd-warshall-algorithm.py

@@ -0,0 +1,29 @@
+from math import inf
+from itertools import product
+
+def floyd_warshall(n, edge):
+    rn = range(n)
+    dist = [[inf] * n for i in rn]
+    nxt  = [[0]   * n for i in rn]
+    for i in rn:
+        dist[i][i] = 0
+    for u, v, w in edge:
+        dist[u-1][v-1] = w
+        nxt[u-1][v-1] = v-1
+    for k, i, j in product(rn, repeat=3):
+        sum_ik_kj = dist[i][k] + dist[k][j]
+        if dist[i][j] > sum_ik_kj:
+            dist[i][j] = sum_ik_kj
+            nxt[i][j]  = nxt[i][k]
+    print("pair     dist    path")
+    for i, j in product(rn, repeat=2):
+        if i != j:
+            path = [i]
+            while path[-1] != j:
+                path.append(nxt[path[-1]][j])
+            print("%d → %d  %4d       %s"
+                  % (i + 1, j + 1, dist[i][j],
+                     ' → '.join(str(p + 1) for p in path)))
+
+if __name__ == '__main__':
+    floyd_warshall(4, [[1, 3, -2], [2, 1, 4], [2, 3, 3], [3, 4, 2], [4, 2, -1]])