poj 3159 Candies (差分约束+spfa)

spfa 的处理 栈比队列快了很多，前几天vongang 说，当时还不信

这题是见证了,队列 直接 RE ，栈 500Ms

#include <iostream>

#include <cstdio>

#include <cstdlib>

#include <cstring>

using namespace std;

#define inf 999999999

#define V 30005

#define E 150005

int n,m;

int  nxt[E],pnt[E],cost[E];

int  vis[V], d[V], head[V];



void init()

{

    int e = 0;

    memset(head, -1, sizeof(head));

    for (int i = 0; i < m; i++)

    {

        int u, v, c;

        scanf("%d%d%d", &u, &v, &c);



        pnt[e] = v; cost[e] = c;

        nxt[e] = head[u]; head[u] = e++;

    }

}



void spfa()

{

    for(int i=0;i<=n;i++)

    d[i]=inf,vis[i]=0;

    vis[1] = 1; d[1] = 0;



    int p[E];

    p[0] = 1;int top = 1;

    while (top)

    {

        int u = p[--top];

        vis[u] = false;

        for (int i = head[u]; i != -1; i = nxt[i])

        {

            int v=pnt[i];

            if (d[v] > d[u] + cost[i])

            {

                d[v] = d[u] + cost[i];

                if (!vis[ v ])

                {

                    p[top++] = v;

                    vis[v] = true;

                }

            }

        }

    }

    printf("%d\n", d[n]);

}



int main()

{

    scanf("%d%d", &n, &m);

    init();

    spfa();

    return 0;

}