Bellman-Ford算法

//Bellman-Ford算法（含有负权的最短路径问题）
#include <stdio.h>

#define MAXM 100
#define MAXN 10

const int INF = 1<<20;

int u[MAXM], v[MAXM], w[MAXM];
int d[MAXN];

int Bellman_Ford(int v0, int n, int m){
    int i, k;
    for(i=0; i<n; i++) d[i] = INF;
    d[v0] = 0;
    for(k=0; k<n-1; k++){
        for(i=0; i<m; i++){
            int x = u[i], y = v[i];
            if(d[x] < INF && d[x]+w[i]<d[y]) d[y] = d[x]+w[i];
        }
    }

    for(i=0; i<m; i++){ //检查是否存在负环
        int x = u[i], y = v[i];
        if(d[x] < INF && d[y] > d[x] + w[i]) return 0;  //如果存在，返回假
    }
    return 1;
}

int main(){
    //freopen("d:\\my.txt", "r", stdin);
    int n, m, i;
    scanf("%d %d", &n, &m);
    for(i=0; i<m; i++) scanf("%d %d %d", &u[i], &v[i], &w[i]);

    if(Bellman_Ford(0, n, m)) printf("%d\n", d[n-1]);
    else printf("ERROR!\n");

    return 0;
}

 较好的一篇介绍Bellman-Ford算法的文章

http://www.360doc.com/content/11/0915/16/7511080_148495650.shtml