HDU1233还是畅通工程

这道题目是很简单的最小生成树的典型例题 。通过这个题目学习Prim算法。

 

#include <iostream>
using namespace std;
int map[102][102], visited[102], lowercost[102], m, n;
#define MAX 0x7fffffff
void init()
{
    int i, j, a, b, c;
    for(i=0; i<n; i++)
        for(j=0; j<n; j++)
            map[i][j] =MAX;
    for(i=0; i<m; i++)
    {
        cin>>a>>b>>c;
        map[a][b] = map[b][a]=c;
    }
    memset(visited,0,sizeof(visited));
    memset(lowercost,0,sizeof(lowercost));
}

int Prim(int v)
{
    int i, j, k, min=0, tmp_min;
    visited[v] = 1;
    for(i=1; i<=n; i++)
        lowercost[i] = map[v][i];
    for(i=2; i<=n; i++)
    {
        tmp_min = MAX;
        
        for(j=1; j<=n; j++)
            if(tmp_min>lowercost[j]&&visited[j]==0)
            {
                v = j;
                tmp_min = lowercost[j];
            }
        visited[v] = 1;
        min+=tmp_min;
        for(j=1; j<=n; j++)
            if(lowercost[j]>map[v][j]&&visited[j]==0)
                lowercost[j] = map[v][j];
    }
    return min;
}


void main()
{
    int i, j;
    while(cin>>n&&n)
    {
        m = (n*(n-1))/2;
        init();
        int min = Prim(1);
        cout<<min<<endl;
    }
}