Bellman_ford最短路

 #include <cstdio>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 #include <cmath>
 #include <queue>
 #define inf 0x3f3f3f3f
 const int maxn = ;
 int n, m, pre[maxn], edge[maxn * maxn][];
 int dist[maxn];
 bool relax(int u, int v, int c){
     if(dist[v] > dist[u] + c){
         dist[v] = dist[u] + c; pre[v] = u;
         return true;
     }
     return  false;
 }
 int bellman(int S){
     int i, j;
     for(i = ; i < n; i ++){
         dist[i] = inf;
         pre[i] = -;
     }
     dist[S] = ;
     bool flag;
     for(i = ;i < n; i ++){
         flag = false;
         for(j = ; j < m; j ++)
             if(relax(edge[j][], edge[j][], edge[j][])) flag = true;
         if(!flag) break;
     }
     for(j = ; j < m; j ++)
         if(relax(edge[j][], edge[j][], edge[j][])) return false;
     return true;
 }