func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m, x, y;     cin >> n >> m;     vector<int> deg(n, 0), uf(n), uf_cnt(n, 1);     for (int i = 0; i < n; ++i) uf[i] = i;     for (int i = 0; i < m; ++i) {       cin >> x >> y;       deg[--x]++;       deg[--y]++;       while (x != uf[x]) x = uf[x];       while (y != uf[y]) y = uf[y];       if (x < y) {         uf_cnt[x] += uf_cnt[y];         uf_cnt[y] = 0;         uf[y] = x;       }       if (y < x) {         uf_cnt[y] += uf_cnt[x];         uf_cnt[x] = 0;         uf[x] = y;       }     }     for (int i = 0; i < n; ++i) {       int j = i;       while (j != uf[j]) j = uf[j];       if (deg[i] + 1 != uf_cnt[j]) {         cout <<  NO n ;         return 0;       }     }     cout <<  YES n ;     return 0;   }   