人活着系列之Streetlights （克鲁斯卡尔）

#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>
#include <math.h>
#include <algorithm>
#define INF 0x3f3f3f3f
const int N = 100010;
using namespace std;

struct node
{
    int u,v,w;
} g[N];
int num = 0,sum = 0,zong = 0,n,m,father[N];
int cmp(const void *a,const void *b)
{
    struct node *X,*Y;
    X = (struct node *)a;
    Y = (struct node *)b;
    return X->w - Y->w;
}
int findx(int r)
{
    while(r != father[r])
    {
        r = father[r];
    }
    int i = r,j;
    while(father[i] != r)
    {
        j = father[i];
        father[i] = r;
        i = j;
    }
    return r;
}

void Kruskal()
{

    for(int i = 0; i < m; i++)
    {
        int uu = findx(g[i].u);
        int vv = findx(g[i].v);
        if(uu!=vv)
        {
            num ++;
            sum += g[i].w;
            father[uu] = vv;
        }
        if(num == n-1)
            break;
    }
}
void init()
{
    zong = 0,num = 0,sum = 0;
    for(int i = 0; i <=n; i++)
        father[i] = i;
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        init();
        for(int i = 0; i < m; i++)
        {
            scanf("%d%d%d",&g[i].u,&g[i].v,&g[i].w);
            zong += g[i].w;
        }
        qsort(g,m,sizeof(g[0]),cmp);

        Kruskal();
        (num==n-1)?printf("%d\n",zong-sum):puts("-1");
    }
}