标签：并查集   贪心   

先对边进行从大到小的排序

并查集保存节点数和长度

Conquer a New Region

4
1 2 2
2 4 1
2 3 1
4
1 2 1
2 4 1
2 3 1

4
3

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <limits.h>
#include <ctype.h>
#include <string.h>
#include <string>
#include <algorithm>
#include <iostream>
#include <queue>
#include <stack>
#include <deque>
#include <vector>
#include <set>
#include <map>
using namespace std;
#define MAXN 200000 + 200
typedef __int64 LL;

struct node{
    LL x;
    LL y;
    LL cost;
}E[MAXN];

LL f[MAXN];//父亲节点
LL dis[MAXN];//与该节点相连所有的点到该节点的权值的和
LL sum[MAXN];//该节点的儿子数

bool cmp(node a,node b){
    return a.cost > b.cost;
}

LL find(LL x){
    if(x == f[x]){
        return x;
    }
    return f[x] = find(f[x]);
}

void init(){
    LL i;
    for(i=0;i<MAXN;i++){
        f[i] = i;
        dis[i] = 0;
        sum[i] = 1;
    }
}

void unio(LL x,LL y,LL v){
    f[x] = y;
    sum[y]+=sum[x];
    dis[y] = v;
}

int main(){
    LL n,i;

    while(~scanf("%I64d",&n)){
        for(i=1;i<n;i++){
            scanf("%I64d%I64d%I64d",&E[i].x,&E[i].y,&E[i].cost);
        }
        sort(E+1,E+n,cmp);
        init();
        for(i=1;i<n;i++){
            LL dx = find(E[i].x);
            LL dy = find(E[i].y);
            LL dis1 = dis[dx]+E[i].cost*sum[dy];//因为E【i】.cost一定要比这两个集合中的任何一条边都要短
            LL dis2 = dis[dy]+E[i].cost*sum[dx];
            if(dis1 > dis2){
                unio(dy,dx,dis1);
            }
            else{
                unio(dx,dy,dis2);
            }
        }
        printf("%I64d\n",dis[find(1)]);
    }

    return 0;
}

并查集+贪心 HDU4424

标签：并查集   贪心   

原文地址：http://blog.csdn.net/zcr_7/article/details/40985565