POJ 3259 Wormholes 最短路径（Bellman Ford）

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Code:

#include <iostream>#include <cstdio>#include <cstring>using namespace std;const int maxm = 2500 * 2 + 200 + 10;const int maxn = 500 + 10;const int INF = 999999;struct Edge{    int s;    int e;    int weight;};Edge M[maxm];int dist[maxn];bool Bellman_Ford( int n, int m, int w ){    for( int i = 0; i < maxn; i++ )        dist[i] = INF;    dist[0] = 0;    for( int i = 0; i < n; i++ )    {        bool flag = true;        for( int j = 0; j < 2 * m + w; j++ )        {            if( dist[M[j].e] > dist[M[j].s] + M[j].weight )            {                dist[M[j].e] = dist[M[j].s] + M[j].weight;                flag = false;            }        }        if( flag )  break;    }    for( int j = 0; j < 2 * m + w; j++ )    {        if( dist[M[j].e] > dist[M[j].s] + M[j].weight )            return true;    }    return false;}int main(){    int f;    int n;    int m;    int w;    scanf( "%d", &f );    while( f-- )    {        scanf( "%d%d%d", &n, &m, &w );        for( int i = 0; i < m; i++ )        {            scanf( "%d%d%d", &M[i].s, &M[i].e, &M[i].weight );            M[i+m].s = M[i].e;            M[i+m].e = M[i].s;            M[i+m].weight = M[i].weight;        }        for( int i = m * 2; i < m * 2 + w; i++ )        {            scanf( "%d%d%d", &M[i].s, &M[i].e, &M[i].weight );            M[i].weight = -M[i].weight;        }        printf( "%s\n", Bellman_Ford( n, m, w ) ? "YES" : "NO" );    }    return 0;}

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