HDU Ice_ Cream's world I

Portal

The question ： Give a n A little bit m A multiplicity free graph with edges , Try to find out the maximum number of non overlapping rings .

Ideas ： Just deform the merge function of the joint search set ~ There is no need to consider whether to take a large ring or a small ring , As long as the newly added edge can form a closed loop , It must be adding a separate ring or dividing an original ring into two , Contributions are 1.

#include<bits/stdc++.h>
#define endl '\n'
#define null NULL
#define ll long long
#define int long long
#define pii pair<int, int>
#define lowbit(x) (x &(-x))
#define ls(x) x<<1
#define rs(x) (x<<1+1)
#define me(ar) memset(ar, 0, sizeof ar)
#define mem(ar,num) memset(ar, num, sizeof ar)
#define rp(i, n) for(int i = 0, i < n; i ++)
#define rep(i, a, n) for(int i = a; i <= n; i ++)
#define pre(i, n, a) for(int i = n; i >= a; i --)
#define IOS ios::sync_with_stdio(0); cin.tie(0);cout.tie(0);
const int way[4][2] = {
   {1, 0}, {-1, 0}, {0, 1}, {0, -1}};
using namespace std;
const int  inf = 0x3f3f3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-6;
const ll   mod = 1e9+7;
const int  N = 2e5 + 5;

inline void read(int &x){
    char t=getchar();
    while(!isdigit(t)) t=getchar();
    for(x=t^48,t=getchar();isdigit(t);t=getchar()) x=x*10+(t^48);
}

int n, m, f[N], ans;

int find(int x)
{
    return x == f[x]?x:f[x] = find(f[x]);
}
int join(int x, int y)
{
    int a = find(x), b = find(y);
    if(a != b){
        f[a] = b;
        return 0;
    }
    return 1; // If the root node is the same , Can form a ring 
}
signed main()
{
    IOS;

    cin >> n >> m;
    for(int i = 0; i < n; i ++) f[i] = i;
    while(m --){
        int u, v; cin >> u >> v;
        ans += join(u, v);
    }
    cout << ans << endl;

    return 0;
}