Kruskal最小生成树

并查集+kruskal==>MST

效率很低

#include <iostream>
using namespace std;

#define MAX 105   //自己设置最大值

// father[x]表示x的父节点
int father[MAX];
// rank[x]表示x的秩
int rank[MAX];

typedef struct
{
    int i,j;
    int distance;
} E;

E edges[MAX*MAX];

// 初始化
void Make_Set(int n)
{
    for(int i=1; i<=n; ++i)
    {
        father[i] = i;
        rank[i] = 0;
    }
}

// 查找
int Find_Set(int x)
{
    if(x != father[x])
        return Find_Set(father[x]);
    return x;
}

// 合并
void Union(int x, int y)
{
    x = Find_Set(x);
    y = Find_Set(y);
    if(x == y)  // x,y在同一个集合
        return;
    if(rank[x] > rank[y])
        father[y] = x;
    else if(rank[x] < rank[y])
        father[x] = y;
    else
    {
        rank[y]++;
        father[x] = y;
    }
}

bool myfunction ( const E a , const E b )
{
    return (a.distance<b.distance);
}

int main()
{
    freopen("input.txt","r",stdin);
    int i,j,n,m,u,v;
    int count,Sum;
    while(cin>>n&&n!=0)
    {
        count=Sum=0;
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
            {
                edges[i*n+j].i=i;
                edges[i*n+j].j=j;
                cin>>edges[i*n+j].distance;
            }
        sort(edges,edges+(n*n),myfunction);
        Make_Set(n);
        for(i=0; i<n*n; i++)
        {
            if(count==n-1) break;
            if(edges[i].i!=edges[i].j&&(Find_Set(edges[i].i)!=Find_Set(edges[i].j)))
               {
                   Union(edges[i].i,edges[i].j);
                   Sum+=edges[i].distance;
               }
        }
        cout<<Sum<<endl;
    }
    return 0;
}