POJ1287 Networking

解题思路：Kruskal模板题，重复输入的情况，本题是无向图。

见代码：

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
#define inf 0x3f3f3f3f
const int maxn = 100005;
int n, m, father[55],w[55][55];

int Find(int x)
{
    return father[x] == x ? x : father[x] = Find(father[x]);
}

struct node{
    int x, y, w;
}p[maxn];

int cmp(node A, node B)
{
    return A.w < B.w;
}

int main()
{
    int a, b, x;
    while(~scanf("%d", &n) && n)
    {
        scanf("%d", &m);
        for(int i = 1; i <= n; i++)
        {
            for(int j = i; j <= n; j++)
            {
                if(i == j) w[i][j] = 0;
                else w[i][j] = w[j][i] = inf;
            }
        }
        for(int i = 0; i < m; i++)
        {
            scanf("%d%d%d", &a, &b, &x);
            p[i].x = a, p[i].y = b, p[i].w = x;
            //如果两点有多条路，这步取更小的值
            if(w[a][b] > x) w[a][b] = w[b][a] = x;
        }
        sort(p, p + m, cmp); //从小到大
        //并查集初始化
        for(int i = 1; i <= n; i++) father[i] = i;
        int sum = 0;
        for(int i = 0; i < m; i++)
        {
            int rootx = Find(p[i].x);
            int rooty = Find(p[i].y);
            //不在同一个集合就加起来
            if(rootx != rooty)
            {
                sum += p[i].w;
                father[rootx] = rooty;
            }
        }
        printf("%d\n", sum);

    }
    return 0;
}