poj 2240 Arbitrage

<span style="background-color: rgb(255, 255, 255);"><strong><span style="font-size:18px;">这是一个货币交换问题，就是问你货币交换之后能不能赚到钱，我用数组存储，G[i][i]存储的是第i种货币交换若干次得到的第i种货币的比率，如果大于1就赚了，否则没有赚；用FLOYED求最大回报</span></strong></span><pre name="code" class="cpp">/*********************************************** * Author: fisty * Created Time: 2015/2/16 21:44:34 * File Name   : four_I.cpp *********************************************** */#include <iostream>#include <cstring>#include <deque>#include <cmath>#include <queue>#include <stack>#include <list>#include <map>#include <set>#include <string>#include <vector>#include <cstdio>#include <bitset>#include <algorithm>using namespace std;#define Debug(x) cout << #x << " " << x <<endl#define Memset(x, a) memset(x, a, sizeof(x))const int INF = 0x3f3f3f3f;typedef long long LL;typedef pair<int, int> P;#define FOR(i, a, b) for(int i = a;i < b; i++)#define MAX_N 1001int n, m;map<string, int> mp;void ID(string s, int i){    mp[s] = i;}double G[MAX_N][MAX_N];int main() {    //freopen("in.cpp", "r", stdin);    cin.tie(0);    ios::sync_with_stdio(false);    int cnt = 1;    while(cin >> n){        if(!n) break;        FOR(i, 1, n+1){            string s;            cin >> s;            ID(s, i);        }        //自己给自己汇率为1,其他为0        FOR(i, 1, n+1){            FOR(j, 1, n+1){                G[i][j] = 0;                if(i == j){                    G[i][j] = 1;                }            }        }        cin >> m;        FOR(i, 0, m){            string u, v;            double cost;            cin >> u >> cost >> v;            int e1 = mp[u];            int e2 = mp[v];            G[e1][e2] = cost ;        }        for(int k = 1;k <= n; k++){            for(int i = 1;i <= n; i++){                for(int j = 1;j <= n; j++){                    if(G[i][j] < G[i][k] * G[k][j])                        G[i][j] = G[i][k] * G[k][j];                }            }        }        int ok = 0;        for(int i = 1;i <= n; i++){            if(G[i][i] > 1){                ok = 1;                break;            }        }        cout << "Case " << cnt++ << ": ";        if(ok) cout << "Yes" << endl;        else cout << "No" <<endl;    }    return 0;}