Problem K: Yikes -- Bikes!

http://acm.upc.edu.cn/problem.php?id=2780

昨天做的题，没过……！！！伤心……
题意：给你n个单位，n-1组关系，让你单位换算……
解题思路：Floyd算法
自己听别人说用Floyd算法，然后自己默默的用有向图写……但是！！！Floyd算法不能用有向图……！所以只能在其相反的转化中标记为负的，在进行时特殊处理一下，最后便利找出能进行单位转化的那组单位，然后进行大小排序，最后就莫名其妙的哦过了……！！！

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <map>
#include <cmath>
#include <cstring>
#include <string>
#include <queue>
#include <stack>
#include <cctype>
#include <set>
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())

typedef long long LL;

using namespace std;

int graph[30][30];
int c[30];
int topo[30];
int n;
int t;
struct Value{
    int x,y;
};

bool cmp(Value a,Value b){
    return a.x > b.x;
}

int main()
{
#ifndef ONLINE_JUDGE
   freopen("in.in","r",stdin);
#endif
    map<string,int>un;
    string name[30];
    while(cin >> n && n){
    for(int i = 1;i <= n;i++){
        cin >> name[i];
        un[ name[i] ] = i;
    }
    memset(graph,0,sizeof(graph));
    for(int i = 1;i <= n-1;i++){
        string str1;
        int num,a,b;
        cin >> str1;
        a = un[str1];
        cin >> str1 >> num >> str1;
        b = un[str1];
        graph[a][b] = num;
        graph[b][a] = -1 *num;
        //cout <<a << " " << b << endl;
    }
    for(int k = 1;k <= n;k++){
        for(int i = 1;i <= n;i++){
            for(int j = 1;j <= n;j++){
                if(i == j || k == i || k == j)
                    continue;
                if(!graph[i][j] &&graph[i][k] &&graph[k][j]){
                    if(graph[i][k] > 0 && graph[k][j] > 0){
                        graph[i][j] = graph[i][k] * graph[k][j];
                        graph[j][i] = -1 * graph[i][k] * graph[k][j];
                    }
                    else if(graph[i][k] < 0 && graph[k][j] < 0){
                        graph[j][i] = graph[i][k] * graph[k][j];
                        graph[i][j] = -1 * graph[i][k] * graph[k][j];
                    }
                    else if(graph[i][k] < 0 && graph[k][j] > 0){
                        if(abs(graph[i][k]) > graph[k][j]){
                            graph[j][i] = abs(graph[i][k]) / graph[k][j];
                            graph[i][j] = -1 * graph[j][i];
                        }
                        else{
                            graph[i][j] = abs(graph[i][k]) / graph[k][j];
                            graph[j][i] = -1 * graph[i][j];
                        }
                    }
                    else{
                        if(graph[i][k] > abs(graph[k][j])){
                            graph[i][j] = graph[i][k] / abs(graph[k][j]);
                            graph[j][i] = -1 * graph[i][j];
                        }
                        else{
                            graph[j][i] = graph[i][k] / abs(graph[k][j]);
                            graph[i][j] = -1 * graph[j][i];
                        }
                    }
                }
            }
        }
    }
    int mark;
    for(int i = 1;i <= n;i++){
        bool flag = 1;;
        for(int j = 1;j <= n;j++){
            if(graph[i][j] < 0){
                flag = 0;
                break;
            }
        }
        if(flag){
            mark = i;
            break;
        }
    }
    Value a[30];
    for(int i = 1;i <= n;i++){
        a[i-1].x = graph[mark][i];
        a[i-1].y = i;
    }
    sort(a,a+n,cmp);
    cout << 1  << name[ a[n-1].y ];
    for(int i = n-2;i > -1;i--){
        cout << " = "<< a[i].x << name[ a[i].y ] ;
    }
    cout << endl;
    }
    return 0;
}