POJ 1860 Currency Exchange（SPFA+邻接矩阵）

(￣▽￣)"

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;

const int eps=1e-7;
const int MAXN=110;
int N,M,S;
double V,Vcur[MAXN],R[MAXN][MAXN],C[MAXN][MAXN];
bool vis[MAXN];
int cntNode[MAXN];

bool SPFA()
{
    queue<int> que;
    int u,v;

    for(int i=1;i<=N;i++)
        Vcur[i]=0,vis[i]=0,cntNode[i]=0;
    Vcur[S]=V;vis[S]=1;cntNode[S]=1;
    que.push(S);

    while(!que.empty())
    {
        u=que.front();que.pop();
        vis[u]=0;

        for(v=1;v<=N;v++)
        {
            if((Vcur[u]-C[u][v])*R[u][v]>Vcur[v]+eps)
            {
                Vcur[v]=(Vcur[u]-C[u][v])*R[u][v];
                if(!vis[v])
                {
                    vis[v]=1;
                    ++cntNode[v];
                    que.push(v);
                    if(cntNode[v]>N)
                        return true;
                }
            }
        }
    }
    return false;
}

int main()
{
    scanf("%d%d%d%lf",&N,&M,&S,&V);
    int a,b;
    double r,c,rr,cc;
    while(M--)
    {
        scanf("%d%d%lf%lf%lf%lf",&a,&b,&r,&c,&rr,&cc);
        R[a][b]=r;C[a][b]=c;
        R[b][a]=rr;C[b][a]=cc;
    }
    if(!SPFA()) printf("NO
");
    else printf("YES
");
    return 0;
}