POJ 1860 Currency Exchange 毫无优化的bellman_ford跑了16Ms，spfa老是WA。。

题目链接： http://poj.org/problem?id=1860

找正环，找最长路，水题，WA了两天了。。

#include <stdio.h>

#include <string.h>



struct Edge

{

    int u, v;

    double r, c;

}edge[210];



int rear, n, m, s;

double v, dist[110];



bool bellman_ford()

{

    memset(dist, 0, sizeof(dist));

    dist[s] = v;

    for(int i = 1; i < n; i++)

        for(int j = 0; j < rear; j++)

            if(dist[edge[j].v] < (dist[edge[j].u]-edge[j].c) * edge[j].r)

                dist[edge[j].v] = (dist[edge[j].u]-edge[j].c) * edge[j].r;



    for(int j = 0; j < rear; j++)

        if(dist[edge[j].v] < (dist[edge[j].u]-edge[j].c) * edge[j].r)

            return 1;

    return 0;

}



int main()

{

    int a, b;

    double rab, cab, rba, cba;

    while(scanf("%d %d %d %lf", &n, &m, &s, &v) != EOF)

    {

        rear = 0;

        while(m--)

        {

            scanf("%d %d %lf %lf %lf %lf", &a, &b, &rab, &cab, &rba, &cba);

            edge[rear++] = (struct Edge){a, b, rab, cab};

            edge[rear++] = (struct Edge){b, a, rba, cba};

        }

        printf("%s\n", bellman_ford() ? "YES" : "NO");

    }

    return 0;

}

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