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");
}
}
}