C - Don’t be cycle

https://atcoder.jp/contests/abc288/tasks/abc288_c

思路

检测出最小环有几个，

然后破掉相同数目的边即可。

检测最小环数目方法：

Code

https://atcoder.jp/contests/abc288/submissions/38629260

链式前向星

https://zhuanlan.zhihu.com/p/343092172

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e6;

struct node{
    int to,next;
}e[maxn];

int cnt;
int nums = 0;
int head[maxn],vis[maxn];

void addnode(int u,int v){
    e[++cnt].to = v;
    e[cnt].next = head[u];
    head[u] = cnt;
}

void dfs(int x, int fa){
    vis[x] = 1;
    
    for(int i = head[x]; i; i=e[i].next){
        int y = e[i].to;
        
        if(y==fa) {
            continue;
        }    
        
        if(vis[y]==0){        
            dfs(y,x);
        } else if(vis[y]==1){
            nums++;    
        } else if(vis[y]==2){
            // 2 status means already cycle counted, so do count again
        }
    }

    vis[x] = 2;
}

int main()
{
    int n,m;
    int u,v;
    
    cin >> n >> m;
    
    for(int i = 1;i <= m;i++){
        cin >> u >> v;
        
        addnode(u,v);
        addnode(v,u);
    }

    for(int i = 1;i <= n;i++){
        if(vis[i]==0){
            dfs(i,-1);
        }
    }
    
    cout << nums << endl;
    
    return 0;
}