POJ 2579 Fiber Network(状态压缩+Floyd)

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <ctime>
#include <cmath>
#include <string>
#include <cstring>
#include <stack>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <set>
using namespace std;

const int INF = 0x3f3f3f3f;
const double eps = 1e-10;
const double PI = acos(-1.0);

const int maxn = 500;
int a[maxn][maxn];
int main()
{
    int n;
    while(~scanf("%d", &n)&&n)
    {
        int u, v;
        memset(a, 0, sizeof(a));
        while(scanf("%d%d", &u, &v)&& (u+v))
        {
            char s[100];
            scanf("%s", s);
            for(int i = 0; i < strlen(s); i++)
                a[u][v] |= 1<<(s[i] - ‘a‘);
        }

        for(int k = 1; k <= n; k++)
            for(int i = 1; i <= n; i++)
                for(int j = 1; j <= n; j++)
                a[i][j] |= a[i][k] & a[k][j];

        while(scanf("%d%d", &u, &v) && (u+v))
        {
                for(int i = ‘a‘; i <= ‘z‘; i++)
                     if(a[u][v] & (1 << (i-‘a‘)))
                     printf("%c",i);
                if(!a[u][v])
                    printf("%c",‘-‘);
                puts("");
        }
        puts("");
    }
    return 0;
}