题目1012：畅通工程(树的并查集以及路径优化)

题目链接：http://ac.jobdu.com/problem.php?pid=1012

详解链接：https://github.com/zpfbuaa/JobduInCPlusPlus

参考代码：

//
//  1012 畅通工程.cpp
//  Jobdu
//
//  Created by PengFei_Zheng on 17/04/2017.
//  Copyright © 2017 PengFei_Zheng. All rights reserved.
//
 
#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <cmath>
#define MAX_SIZE 1010
 
using namespace std;
 
int n, m;
int Tree[MAX_SIZE];
 
int findRoot(int x){//find the root of x
    if(Tree[x]==-1) return x;
    else{
        int tmp = findRoot(Tree[x]);//continue the find
        Tree[x] = tmp;//change the root of x to tmp
        return tmp;
    }
     
}
int main(){
    while(scanf("%d",&n)!=EOF && n!=0){//when n==0 and jump out of the loop
        scanf("%d",&m);
        for(int i = 1 ; i <= n ; i++)//init
            Tree[i] = -1;
         
        while(m--){
            int a,b;
            scanf("%d%d",&a,&b);
            a = findRoot(a);//find the root of a
            b = findRoot(b);//find the root of b
            if(a!=b) Tree[a]=b;//merge those two sets to the same aggregates
        }
         
        int ans = 0 ;
        for(int i = 1 ; i <= n ; i++){
            if(Tree[i]==-1) ans++;//calculate the total numbers of aggregates
        }
        printf("%d
",ans-1);
    }
    return 0;
}
/**************************************************************
    Problem: 1012
    User: zpfbuaa
    Language: C++
    Result: Accepted
    Time:10 ms
    Memory:1524 kb
****************************************************************/