hdu_1596

//最短路，只不过这里是乘法，和加法做法一样//这题精度不强#include <cstdio>#include <cstring>#include <queue>#include <algorithm>using namespace std;#define MAXN    1001#define INF     0x3f3f3f3fint     in_queue[MAXN];double  dis[MAXN], each_dis[MAXN][MAXN], ans;double spfa(int src, int des, int vertex){        int u, v;        queue<double> q;        memset(dis, 0, sizeof(dis));        memset(in_queue, 0, sizeof(in_queue));        q.push(src); in_queue[src] = 1;        while( !q.empty() ) {                u = q.front(); q.pop(); in_queue[u] = 0;                for(v = 1; v <= vertex; v ++) {                        if( 0.0 == each_dis[u][v] ) {                                continue;                        }                        if( dis[v] < ((0.0 == dis[u])?1 : dis[u])*each_dis[u][v] ) {                                dis[v] = ((0.0 == dis[u])?1 : dis[u])*each_dis[u][v];                                if( !in_queue[v] ) {                                        q.push(v);                                }                        }                }        }        return (0.0 == dis[des])? -1 : dis[des];}int main(int argc, char const *argv[]){#ifndef ONLINE_JUDGE        freopen("test.in", "r", stdin);#endif        int vertex, ask, u, v;        while( ~scanf("%d", &vertex) ) {                memset(dis, 0, sizeof(dis));                for(int i = 1; i <= vertex; i ++) {                        for(int j = 1; j <= vertex; j ++) {                                scanf("%lf", &each_dis[i][j]);                        }                }                scanf("%d", &ask);                for( ; ask; ask --) {                        scanf("%d %d", &u, &v);                        ans = spfa(u, v, vertex);                        if( -1.0 == ans ) {                                printf("What a pity!\n");                        }                        else {                                printf("%.3lf\n", ans);                        }                }        }        return 0;}