差分约束+SPFA+栈

#include <stdio.h>
#include <string.h>
#include <queue>
#include <stack>
#define INF 0x3f3f3f3f
using namespace std;
struct node
{
    int u,v,w,next;
}edge[150001];
int head[30001],dis[30001],vis[30001],k,n,m,s;

void add(int u,int v,int w)
{
    edge[k].u = u;
    edge[k].v = v;
    edge[k].w = w;
    edge[k].next = head[u];
    head[u] = k++;
}

void SPFA()
{
    int i;
    int tt,vv;
    for(i = 1;i<=n;i++)
    {
        dis[i] = INF;
        vis[i] = 0;
    }
    dis[s] = 0;
    vis[s] = 1;
     // queue<int>q;
     stack<int>q;
    while(!q.empty())
    {
        q.pop();
    }
    q.push(s);
    while(!q.empty())
    {
       // tt = q.front();
       tt = q.top();
        q.pop();
        vis[tt] = 0;
        for(i = head[tt];i!=-1;i = edge[i].next)
        {
            vv = edge[i].v;
            if(dis[vv]>dis[tt] + edge[i].w)
            {
                dis[vv] = dis[tt] + edge[i].w;
                if(!vis[vv])
                {
                    vis[vv] = 1;
                    q.push(vv);
                }
            }
        }
    }

}
int main()
{
    int i,u,v,w;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        s = 1;
        for(i = 1;i<=n;i++)
        {
            head[i] = -1;
        }
        k = 0;
        for(i = 0;i<m;i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            add(u,v,w);
        }
        SPFA();
        printf("%d
",dis[n]);
    }
    return 0;
}

http://acm.sdut.edu.cn:8080/vjudge/contest/view.action?cid=267#problem/C