hdu 1596 find the safest road (dijkstra)

find the safest road

题目链接：Problem - 1596

题目大意：略

题目分析：水题，此题数据少，属于稠密图，可以用dijkstra做

思路分析：

1）double 数组存图

2）读取出发点和到达点，用dijkstra算法计算出最优路径

3）若路径不存在，输出“What a pity!"

贴AC代码： 

#include <stdio.h> //定义输入／输出函数#include <limits.h> //定义各种数据类型最值常量#include <math.h> //定义数学函数#include <stdlib.h> //定义杂项函数及内存分配函数#include <string.h> //字符串处理#include <algorithm>//算法#include <queue>//队列#include <stack>//栈#include <vector>using namespace std;int n, Q, from, to, tmp;double map[1005][1005];double low[1005];bool vis[1005];void dijkstra(){    memset(low, 0, sizeof(low));    memset(vis, 0, sizeof(vis));    for (int i = 1; i <= n; i++){        if (map[from][i] == 0) continue;        low[i] = map[from][i];    }    vis[from] = 1;    for (int i = 0; i < n - 1; i ++){        double maxs = 0;        for (int j = 1; j <= n; j++){            if (low[j] > maxs && vis[j] == 0){                maxs = low[j];                tmp = j;            }        }        vis[tmp] = 1;        //printf("：：%d || tmp = %d\n", i, tmp);        //for (int k = 1; k <= n;k ++)        //    printf("%.3f ", low[k]);        //printf("\n\n");        for (int j = 1; j <= n; j++){            if (map[tmp][j] == 0) continue;            if (low[j] < low[tmp] * map[tmp][j])                low[j] = low[tmp] * map[tmp][j];        }    }}int main(){    while (scanf("%d", &n) != EOF && n){        for (int i = 1; i <= n; i ++)            for (int j = 1; j <= n; j++)                scanf("%lf", &map[i][j]);        scanf("%d", &Q);        while (Q--){            scanf("%d%d", &from, &to);            dijkstra();            if (low[to] != 0.0) printf("%.3f\n", low[to]);            else printf("What a pity!\n");        }    }}