fix

Algorithms/Graph/NetworkFlow/ISAP_no_pointers.cpp

@@ -18,7 +18,7 @@ int ISAP(int s, int e)
     int h = 0, t = 0, x;
     for (int i = 1; i <= n; i++) d[i] = n;
     d[que[t++] = e] = 0;
-    while (h != t) for (int i = head[x = que[h++]]; i; i = next[i])
+    while (h != t) for (int i = head[x = que[h++]]; ~i; i = next[i])
         if (cap[i ^ 1] > 0 && d[to[i]] > d[x] + 1)
             d[que[t++] = to[i]] = d[x] + 1;
     memset(num, 0, sizeof(num));