ccf算法模板

bellman ford 算法求最短路径

 #include <iostream>
 using namespace std;
 const int maxnum = ;
 const int maxint = ;

 // 边，
 typedef struct Edge{
     int u, v;    // 起点，重点
     int weight;  // 边的权值
 }Edge;

 Edge edge[maxnum];     // 保存边的值
 int  dist[maxnum];     // 结点到源点最小距离

 int nodenum, edgenum, source;    // 结点数，边数，源点

 // 初始化图
 void init()
 {
     // 输入结点数，边数，源点
     cin >> nodenum >> edgenum >> source;
     for (int i = ; i <= nodenum; ++i)
         dist[i] = maxint;
     dist[source] = ;
     for (int i = ; i <= edgenum; ++i)
     {
         cin >> edge[i].u >> edge[i].v >> edge[i].weight;
         if (edge[i].u == source)          //注意这里设置初始情况
             dist[edge[i].v] = edge[i].weight;
     }
 }

 // 松弛计算
 void relax(int u, int v, int weight)
 {
     if (dist[v] > dist[u] + weight)
         dist[v] = dist[u] + weight;
 }

 bool Bellman_Ford()
 {
     for (int i = ; i <= nodenum - ; ++i)
     for (int j = ; j <= edgenum; ++j)
         relax(edge[j].u, edge[j].v, edge[j].weight);
     bool flag = ;
     // 判断是否有负环路
     for (int i = ; i <= edgenum; ++i)
     if (dist[edge[i].v] > dist[edge[i].u] + edge[i].weight)
     {
         flag = ;
         break;
     }
     return flag;
 }
 int main()
 {
     //freopen("input3.txt", "r", stdin);
     init();
     if (Bellman_Ford())
     for (int i = ; i <= nodenum; i++)
         cout << dist[i] << endl;
     return ;
 }