数据结构实验之图论十一：AOE网上的关键路径【Bellman_Ford算法】

#include <bits/stdc++.h>

using namespace std;

struct node
{
    int u,v,w;
}a[50010];
int path[50010];
int dist[50010];
int from[50010];
int to[50010];
void bellman_ford(int s, int n, int m)
{
    memset(path,0,sizeof(path));
    memset(dist,0,sizeof(dist));
    int f = 0;
    for(int i = 2; i <= n; i ++)
    {
        f = 0;
        for(int j = 1; j <= m; j ++)
        {
            int u = a[j].u;
            int v = a[j].v;
            int w = a[j].w;
            if(dist[u] < dist[v] + w || (dist[u] == dist[v] + w && v < path[u]))
            {
                dist[u] = dist[v] + w;
                path[u] = v;
                f = 1;
            }
        }
        if(f == 0) break;
    }
   // cout << s <<endl;
    printf("%d\n",dist[s]);
    int k = s;
    while(path[k] != 0)
    {
        printf("%d %d\n",k,path[k]);
        k = path[k];
    }
}
int main()
{
    int n,m,u,v,w,s;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(a,0,sizeof(a));
        memset(from,0,sizeof(from));
        memset(to,0,sizeof(to));
        for(int i = 1; i <= m; i ++)
        {
                scanf("%d%d%d",&u,&v,&w);
                a[i].u = u;
                a[i].v = v;
                a[i].w = w;
                from[u] ++;
                to[v] ++;
        }
        for(int i = 1; i <= n; i ++)
        {
            if(to[i] == 0)
            {
                s = i;
                break;
            }
        }
        bellman_ford(s,n,m);
    }
    return 0;
}