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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. int main(){
  4. int n;
  5. cin>>n;
  6. int a[n+1];
  7. for(int i=1;i<=n;i++){
  8.    cin>>a[i];
  9. }
  10. int f=0;
  11. deque<int> q;
  12. int u=a[1];
  13. //cout<<u<<endl;
  14. int mx=a[1];
  15. for(int k=1;k<u;k++)q.push_front(k);
  16. for(int i=2;i<=n;i++){
  17.    if(a[i]>a[i-1]){
  18.       mx = max(mx,a[i-1]);
  19.        int j = mx+1;
  20.        while(j<a[i]){
  21.          q.push_front(j);
  22.          j++;
  23.        }
  24.    }
  25.    else{
  26.       if(a[i]==q.front()&&!q.empty()){
  27.          q.pop_front();
  28.       }
  29.       else{
  30.          f=1;
  31.          break;
  32.       }
  33.    }
  34. }
  35. if(f==1)cout<<"NO\n";
  36. else cout<<"YES\n";
  37.  
  38. }
Runtime error #stdin #stdout 0s 4304KB
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stdin
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/FyQPjH
language:
C++14 (gcc 8.3)
created:
3 years ago
visibility:
public

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