spfa

 1 int spfa(int s,int t) {
 2     memset(d, 0x3f, sizeof(d));
 3     d[s] = 0;
 4     v[s] = 1;
 5     q.push(s);
 6     while (q.size()) {
 7         int x = q.frout();
 8         q.pop();
 9         v[x] = 0;
10         for (int i = h[x]; i; i = e[i].n) {
11             if (d[e[i].t] > d[x] + e[i].w) {
12                 d[e[i].t] = d[x] + e[i].w;
13                 if (v[e[i].t] == 0) {
14                     v[e[i]].t=1;
15                     q.push(e[i].t);
16                 }
17             }
18         }
19     }
20     return d[t] == 0x3f ? -1 : d[t];
21 }