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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     int n, k;
  6.     cin >> n >> k;
  7.     vector<int> a(n), lg(n), rg(n);
  8.     for (int &x : a) cin >> x;
  9.     lg[0] = 1;
  10.     rg[n - 1] = 1;
  11.  
  12.     int ma = 0;
  13.     for (int i = 0; i < n - 1; i++) {
  14.         ma = max(ma, a[i]);
  15.         if (a[i + 1] >= ma) rg[i] = 1;
  16.     }
  17.  
  18.     int mi = n;
  19.     for (int i = n - 1; i > 0; i--) {
  20.         mi = min(mi, a[i]);
  21.         if (a[i - 1] <= mi) lg[i] = 1;
  22.     }
  23.  
  24.     int flag = 1;
  25.     for (int i = 1; i < n - 1; i++) {
  26.         if (flag && a[i - 1] <= a[i]) lg[i + 1] &= 1;
  27.         else lg[i + 1] = flag = 0;
  28.     }
  29.  
  30.     flag = 1;
  31.     for (int i = n - 2; i > 0; i--) {
  32.         if (flag && a[i] <= a[i + 1]) rg[i - 1] &= 1;
  33.         else rg[i - 1] = flag = 0;
  34.     }
  35.  
  36.     for (int i = k - 1; i < n; i++) {
  37.         if (rg[i] && lg[i - k + 1]) {
  38.             cout << "Yes\n";
  39.             return 0;
  40.         }
  41.     }
  42.     cout << "No\n";
  43. }
  44.  
Success #stdin #stdout 0.01s 5324KB
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Standard input is empty
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Yes
https://ideone.com/r7wubg
language:
C++ (gcc 8.3)
created:
4 days ago
visibility:
public

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