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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4. const int MAXN = 1e6 + 10;
  5. int parent[MAXN],n,x,y,k,size[MAXN];
  6. int find_root(int v){
  7.      if (v == parent[v])
  8.         return v;
  9.     return find_root(parent[v]);
  10. }
  11. void make_set(int v) {
  12.     parent[v] = v;
  13.     size[v] = 1;
  14. }
  15. void union_sets(int a, int b) {
  16.     a = find_root(a);
  17.     b = find_root(b);
  18.     if (a != b) {
  19.         if (size[a] < size[b])
  20.             swap(a, b);
  21.         parent[b] = a;
  22.         size[a] += size[b];
  23.     }
  24. }
  25. bool check(int u, int v){
  26.     return (find_root(u)==find_root(v));
  27. }
  28. int main()
  29. {
  30.     cin>>n>>k;
  31.     for (int i=1;i<=n;i++) make_set(i);
  32.     for (int i=0;i<k;i++){
  33.         cin>>x>>y;
  34.         if (x>y) swap(x,y);
  35.         union_sets(x,y);
  36.     }
  37.     for (int i=1;i<=(n+1)/2;i++) if (!check(i,n-i+1)) {
  38.         cout<<"No";
  39.         return 0;
  40.     }
  41.     cout<<"Yes";
  42.     return 0;
  43. }
Success #stdin #stdout 0s 23048KB
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Standard input is empty
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Yes
https://ideone.com/OU0mBd
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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