poj 2485 Highways

Highways

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 28525		Accepted: 13006

DescriptionThe island nation of Flatopia is perfectly flat. Unfortunately, Flatopia has no public highways. So the traffic is difficult in Flatopia. The Flatopian government is aware of this problem. They're planning to build some highways so that it will be possibleto drive between any pair of towns without leaving the highway system. Flatopian towns are numbered from 1 to N. Each highway connects exactly two towns. All highways follow straight lines. All highways can be used in both directions. Highways can freely cross each other, but a driver can only switch between highways at a townthat is located at the end of both highways. The Flatopian government wants to minimize the length of the longest highway to be built. However, they want to guarantee that every town is highway-reachable from every other town.InputThe first line of input is an integer T, which tells how many test cases followed. The first line of each case is an integer N (3 <= N <= 500), which is the number of villages. Then come N lines, the i-th of which contains N integers, and the j-th of these N integers is the distance (the distance should be an integer within [1, 65536]) betweenvillage i and village j. There is an empty line after each test case.OutputFor each test case, you should output a line contains an integer, which is the length of the longest road to be built such that all the villages are connected, and this value is minimum.Sample Input

1

3
0 990 692
990 0 179
692 179 0

Sample Output

692

这题就是找最短路中的最大长度

还是用prim算法

下面是代码

#include <stdio.h>#include <string.h>#include <algorithm>#include <iostream>using namespace std;int a[10002][10002];int book[10002];int dis[10002];int main(){    int n,m,i,j;    scanf("%d",&m);    while(m--)    {    scanf("%d",&n);        for(i = 0;i < n;i++)        {            for(j = 0;j < n; j++)            {                scanf("%d",&a[i][j]);            }        }        for(i = 0;i < n; i++)        {            dis[i] = a[0][i];        }        memset(book,0,sizeof(book));        book[0] = 1;        int max1 = 0;        int k;        for(i = 0;i < n-1; i++)        {            int min1 = (1<<20);             for(j = 0;j < n; j++)             {                 if(dis[j] < min1&&book[j] == 0)                 {                     k = j;                     min1 = dis[j];                 }             }             max1 = max(max1,min1);     //更新最大边就行             book[k] = 1;             for(j = 0;j < n; j++)             {                 if(dis[j] > a[j][k])                 {                     dis[j] = a[j][k];                 }             }        }        printf("%d\n",max1);    }}

代码菜鸟，如有错误，请多包涵！！