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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. void solve() {
  5.     int n;
  6.     cin >> n;
  7.     vector<int> a(n);
  8.     for (int i = 0; i < n; i++) {
  9.         cin >> a[i];
  10.     }
  11.  
  12.     vector<int> inv;
  13.     for (int i = 0; i < n - 1; i++) {
  14.         if (a[i] > a[i + 1]) {
  15.             inv.push_back(i);
  16.         }
  17.     }
  18.  
  19.     if (inv.empty()) {
  20.         cout << "YES\n";
  21.         return;
  22.     }
  23.  
  24.     long long L = 0;
  25.     for (int i : inv) {
  26.         L = max(L, (long long)a[i] - a[i + 1]);
  27.     }
  28.  
  29.     long long R = 2e18; 
  30.     for (size_t i = 0; i < inv.size() - 1; i++) {
  31.         int left = inv[i] + 1;
  32.         int right = inv[i + 1];
  33.  
  34.         long long mx_diff = -1;
  35.         for (int j = left; j < right; j++) {
  36.             mx_diff = max(mx_diff, (long long)a[j + 1] - a[j]);
  37.         }
  38.  
  39.         if (mx_diff == -1) {
  40.             R = -1;
  41.             break;
  42.         }
  43.         R = min(R, mx_diff);
  44.     }
  45.  
  46.     if (R != -1 && L <= R) {
  47.         cout << "YES\n";
  48.     } else {
  49.         cout << "NO\n";
  50.     }
  51. }
  52.  
  53. int main() {
  54.     ios_base::sync_with_stdio(false);
  55.     cin.tie(NULL);
  56.     int t;
  57.     cin >> t;
  58.     while (t--) {
  59.         solve();
  60.     }
  61.     return 0;
  62. }
Success #stdin #stdout 0s 5328KB
comments (?)
stdin
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8
4
1 2 3 4
5
10 5 9 4 4
7
8 3 9 4 10 5 11
6
5 3 10 5 9 7
3
2 1 1
5
2 1 1 2 1
3
3 1 2
5
2 1 2 3 1
stdout
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YES
NO
YES
NO
YES
YES
YES
NO
https://ideone.com/SDqKU0
language:
C++ (gcc 8.3)
created:
1 hour ago
visibility:
public

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