【POJ】1860 Currency Exchange

真是气skr人。。没把d[]换成double。。。de了一上午的bug//

记得用G++提交啊

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题目链接：http://poj.org/problem?id=1860

题意：告诉你n个点，m条路。起始点s,还有初始金额money。每条路表示从a->b的汇率和佣金以及b->a的汇率和佣金。你在该点所得是（本金-佣金）*汇率。问你这个人能不能赚钱。

题解：spfa套一下//。记得d[]换成double。具体的看看代码。QWQ。

代码：

#include<iostream>
#include<stack>
#include<vector>
#include<queue>
#include<algorithm>
#include<cstdio>
using namespace std;
const int maxn = 105;


struct node{
    int to;
    double r;
    double c;
};

vector< node > e[maxn];

int n,m,num;
double money;
double d[maxn];
int inq[maxn];

bool spfa(int s){
    for(int i = 1; i <= n ;i++){
        inq[i] = d[i] = 0;
    }
    queue<int>Q;
    Q.push(s);
    d[s] = money;
    inq[s] = 1;
    while( !Q.empty() ){
        int now = Q.front();
        Q.pop();
        inq[now] = 0;
        for(int i = 0; i < e[now].size() ; i++){
            double rate = e[now][i].r;
            double commis = e[now][i].c;
            int v = e[now][i].to;

            if(d[v] < (d[now] - commis) * rate){
                d[v] = (d[now] - commis) * rate;
                if(inq[v] == 0){
                    inq[v] = 1;
                    Q.push(v);
                }   
            }

            if(d[s] > money){
                return true;
            }
        }


    }
    return false;
}

int main() {
    scanf("%d%d%d%lf",&n,&m,&num,&money);
    int x,y;
    double r,c;
    while(m--){
        scanf("%d%d%lf%lf",&x,&y,&r,&c);
        e[x].push_back((node){y,r,c});
        scanf("%lf%lf",&r,&c);
        e[y].push_back((node){x,r,c});
    } 
    if(spfa(num))   
        cout<<"YES"<<endl;
    else    
        cout<<"NO"<<endl;   

    return 0;
}