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  1. #include <iostream>
  2. #include <algorithm>
  3. #include <cmath>
  4. #include <cstdio>
  5. #include <stack>
  6.  
  7. using namespace std;
  8.  
  9. int n,a[1001];
  10. stack<int> s;
  11. bool nores;
  12.  
  13. int main() {
  14.     //freopen("test.in","r",stdin);
  15.     while (cin>>n){
  16.         if (n==0) break;
  17.         while (!s.empty()) s.pop();
  18.         for(int i=1; i<=n; i++) cin >> a[i];
  19.         int current=1;
  20.         int i=1;
  21.         nores=false;
  22.         while (current<=n && i<=n){
  23.             if (!s.empty()){
  24.                 while (!s.empty() && s.top()==current) {
  25.                     s.pop();
  26.                     current++;
  27.                     }
  28.                 }
  29.                 while (i<=n && a[i]!=current){
  30.                     s.push(a[i]);
  31.                     i++;
  32.                 }
  33.                 if (i<=n) {
  34.                         i++;
  35.                         current++;
  36.                 }
  37.                 else
  38.                 if (!s.empty() && s.top()!=current) {
  39.                     nores=true;
  40.                 }
  41.             }
  42.  
  43.         if (nores) cout << "no";
  44.         else
  45.             cout << "yes";
  46.         cout << endl;
  47.         }
  48.  
  49. }
  50.  
Success #stdin #stdout 0s 3440KB
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https://ideone.com/7DNddh
language:
C++ (gcc 8.3)
created:
9 years ago
visibility:
public

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