E. Cyclic Components
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হিন্টঃ প্রতিটি কম্পোনেন্ট এ চেক করবো তাদের প্রত্যেকটি নোডের ডিগ্রি দুই কিনা, যদি দুই হয় তাইলে সেটা একটা সিঙ্গেল সাইকেল কম্পোনেন্ট।
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| #include<bits/stdc++.h> | |
| using namespace std; | |
| typedef long long LL; | |
| const int maxn = 200005; | |
| bool visit[maxn]; | |
| vector<int>graph[maxn], curr_graph; | |
| int degree[maxn]; | |
| void dfs(int u) | |
| { | |
| visit[u] = true; | |
| curr_graph.push_back(u); | |
| for(auto v : graph[u]) | |
| { | |
| if(!visit[v]) | |
| dfs(v); | |
| } | |
| } | |
| int countSingleCycles(int n) | |
| { | |
| int cnt = 0; | |
| for(int i = 1; i <= n; i++) | |
| { | |
| if(!visit[i]) | |
| { | |
| curr_graph.clear(); | |
| dfs(i); | |
| int flag = 1; | |
| for(auto v: curr_graph) | |
| { | |
| if(degree[v] == 2)continue; | |
| else | |
| { | |
| flag = 0; | |
| break; | |
| } | |
| } | |
| if(flag)cnt++; | |
| } | |
| } | |
| return cnt; | |
| } | |
| int main() | |
| { | |
| //freopen("in.txt", "r", stdin); | |
| ios_base::sync_with_stdio(false); | |
| cin.tie(0); | |
| int n,m; | |
| cin >> n >> m; | |
| for(int i = 0; i < m; i++) | |
| { | |
| int u,v; | |
| cin >> u >> v; | |
| graph[u].push_back(v); | |
| graph[v].push_back(u); | |
| degree[u]++; | |
| degree[v]++; | |
| } | |
| cout << countSingleCycles(n)<<endl; | |
| return 0; | |
| } | |
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