HDU1596:find the safest road(Dijkstra)

find the safest road

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
using namespace std;

const double inf = 1000000;
int n, m;
double map[1005][1005], cast[1005];
int x, y, vis[1005];

void Dijkstra(int s, int e) {
    int i, j, pos;
    double maxn;
    int flag = 0;

    for(i = 1; i <= n; i++) {
        vis[i] = 0;
        cast[i] = map[s][i];
    }

    vis[s] = 1;
    for(i = 1; i < n; i++) {
        pos = s;
        maxn = 0;

        for(j = 1; j <= n; j++) {
            if(cast[j] > maxn && !vis[j]) {
                pos = j;
                maxn = cast[j];
            }
        }

        if(fabs(maxn) <= 10e-6) {
            flag = 1;
            break;
        }

        vis[pos] = 1;
        for(j = 1; j <= n; j++) {
            if(!vis[j] && map[pos][j] > 0 && cast[pos]*map[pos][j] > cast[j])
                cast[j] = cast[pos] * map[pos][j];
        }
    }

    if(flag)
        printf("What a pity!\n");
    else
        printf("%.3lf\n", cast[e]);
}

int main() {
    freopen("data.in", "r", stdin);

    int i ,j;
    double w;
    while(~scanf("%d", &n)) {
        for(i = 1; i <= n; i++)
            for(j = 1; j <= n; j++)
                scanf("%lf",&map[i][j]);

        scanf("%d",&m);
        while(m--) {
            scanf("%d%d", &x, &y);
            Dijkstra(x, y);
        }
    }

    return 0;
}