D - Unicyclic Components

D - Unicyclic Components

https://atcoder.jp/contests/abc292/tasks/abc292_d

 

思路

并查集，统计连通子图，

并记录edges 数 和 vertices数。

 

CANKAO:

https://blog.csdn.net/karry_zzj/article/details/69831345

Code

https://atcoder.jp/contests/abc292/submissions/39448148

#include <iomanip>
#include <bits/stdc++.h>
#include <iostream>
using namespace std;
#include <limits.h>
#include <math.h>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>

#include<cstdio>
#include<cstring>
using namespace std;

const int maxn = 200000+10;

int V,E;
int pre[maxn];
int vcnt[maxn];
int lcnt[maxn];

/*初始化*/
void init()
{
    for(int i=1; i<=V; i++)
    {
        pre[i] = i;
        vcnt[i] = 1;
        lcnt[i] = 0;
    }
}

/*查找根节点*/
int find(int x)
{
    int r = x;
    while(r!=pre[r])
    r = pre[r];

    int i = x;//路径压缩
    int j;
    while(i != r)
    {
        j = pre[i];
        pre[i] = r;
        i = j;
    }
    
    return r;
}

int main()
{
    scanf("%d%d",&V,&E);

    init();

    int s,t;

    for(int i=0;i<E;i++)
    {
        scanf("%d%d",&s,&t);

        int fx = find(s);
        int fy = find(t);

        if(fx != fy)
        {
            pre[fy] = fx;

            vcnt[fx] += vcnt[fy];
            vcnt[fy] = 0;

            lcnt[fx] += lcnt[fy];
            lcnt[fy] = 0;

            lcnt[fx]++;

        } else {
            lcnt[fx]++;
        }
    }

    for(int i=1; i<=V; i++)
    {
        if(pre[i]==i)
        {
            if (lcnt[i] != vcnt[i]){
                cout << "No" << endl;
                return 0;
            }
        }
    }
    
    cout << "Yes" << endl;
    
    return 0;
}