hdu-1233 还是畅通工程---MST模板

题目链接：

http://acm.hdu.edu.cn/showproblem.php?pid=1233

题目大意：

求MST最小生成树

解题思路：

Prim算法直接套即可

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 100 + 10;
const int INF = 1e9 + 7;
int Map[maxn][maxn];
int lowcost[maxn], mst[maxn];
int n, m;
void prim(int u)
{
    ll ans = 0;
    for(int i = 1; i <= n; i++)
    {
        lowcost[i] = Map[u][i];
        mst[i] = u;
    }
    mst[u] = -1;
    for(int i = 1; i <= n; i++)
    {
        int minn = INF;
        int v = -1;
        //寻找lowcost数组里面的未加入mst的最小值
        for(int j = 1; j <= n; j++)
        {
            if(mst[j] != -1 && lowcost[j] < minn)
            {
                v = j;
                minn = lowcost[j];
            }
        }
        if(v != -1)
        {
            mst[v] = -1;
            ans += lowcost[v];
            for(int j = 1; j <= n; j++)
            {
                if(mst[j] != -1 && lowcost[j] > Map[v][j])
                {
                    lowcost[j] = Map[v][j];
                    mst[j] = v;
                }
            }
        }
    }
    printf("%lld
", ans);
}
int main()
{
    while(scanf("%d", &n) != EOF && n)
    {
        m = n * (n - 1) / 2;
        int u, v, w;
        memset(Map, 0, sizeof(Map));
        memset(lowcost, 0, sizeof(lowcost));
        while(m--)
        {
            scanf("%d%d%d", &u, &v, &w);
            Map[u][v] = Map[v][u] = w;
        }
        prim(1);
    }
    return 0;
}