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  1. /*
  2. * @Author: hungeazy
  3. * @Date:   2025-11-14 23:30:22
  4. * @Last Modified by:   hungeazy
  5. * @Last Modified time: 2025-11-15 07:33:26
  6. */
  7. #include <bits/stdc++.h>
  8. #include <ext/pb_ds/assoc_container.hpp> 
  9. #include <ext/pb_ds/tree_policy.hpp> 
  10. // #pragma GCC optimize("O3")  
  11. // #pragma GCC optimize("unroll-loops")  
  12. // #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")  
  13. using namespace std;
  14. using namespace __gnu_pbds; 
  15. bool M1;
  16. #define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
  17. #define int long long
  18. #define ll long long 
  19. #define ull unsigned long long
  20. #define sz(x) x.size()
  21. #define sqr(x) (1LL * (x) * (x))
  22. #define all(x) x.begin(), x.end()
  23. #define fill(f,x) memset(f,x,sizeof(f))
  24. #define FOR(i,l,r) for(int i=l;i<=r;i++)
  25. #define FOD(i,r,l) for(int i=r;i>=l;i--)
  26. #define debug(x) cout << #x << " = " << x << '\n'
  27. #define ii pair<int,int>
  28. #define iii pair<int,ii>
  29. #define di pair<ii,ii>
  30. #define vi vector<int>
  31. #define vii vector<ii>
  32. #define mii map<int,int>
  33. #define fi first
  34. #define se second
  35. #define pb push_back
  36. #define MOD 1000000007
  37. #define __lcm(a,b) (1ll * ((a) / __gcd((a), (b))) * (b))
  38. #define YES cout << "YES\n"
  39. #define NO cout << "NO\n"
  40. #define MASK(i) (1LL << (i))
  41. #define c_bit(i) __builtin_popcountll(i)
  42. #define BIT(x,i) ((x) & MASK(i))
  43. #define SET_ON(x,i) ((x) | MASK(i))
  44. #define SET_OFF(x,i) ((x) & ~MASK(i))
  45. #define oo 1e18
  46. #define name "TIEUPHU"
  47. #define endl '\n'
  48. #define memory() cerr << abs(&M2-&M1)/1024.0/1024 << " MB" << endl
  49. #define time() cerr << endl << "-------------Time:" << 1000.0 * clock() / CLOCKS_PER_SEC << "ms." << endl
  50. template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
  51. template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
  52. template <class T> using ordered_set = tree <T, null_type, less_equal <T>, rb_tree_tag,tree_order_statistics_node_update>;
  53. const int N = (int)1e7+10;
  54. int n,h[N];
  55.  
  56. namespace sub2 {
  57.  
  58. 	bool approved() {
  59. 		return n <= 1e3;
  60. 	}
  61.  
  62. 	void solve(void)
  63. 	{
  64. 		FOR(i,1,n)
  65. 		{
  66. 			int val = i, prev = 1;
  67. 			bool ok = true;
  68. 			FOR(j,1,n)
  69. 				if (h[j] >= val)
  70. 				{	
  71. 					if (j-prev > val) 
  72. 					{
  73. 						ok = false;
  74. 						break;
  75. 					}
  76. 					prev = j;
  77. 				}
  78. 			if (ok)
  79. 			{
  80. 				cout << i;
  81. 				return;
  82. 			}
  83. 		}
  84. 	}
  85.  
  86. }
  87.  
  88. namespace sub5 {
  89.  
  90. 	void solve(void)
  91. 	{
  92. 		int ans = 0;
  93. 		stack<int> st;
  94. 		st.push(n);
  95. 		FOD(i,n,1)
  96. 			if (i+h[i] >= st.top())
  97. 			{
  98. 				maximize(ans,st.top()-i);
  99. 				while (!st.empty() and h[st.top()] < ans)
  100. 				{
  101. 					st.pop();
  102. 					maximize(ans,st.top()-i);
  103. 				}
  104. 				st.push(i);
  105. 			}		
  106. 		cout << ans;
  107. 	}
  108.  
  109. }
  110.  
  111. bool M2;
  112. signed main()
  113. {
  114.     fast;
  115.     if (fopen(name".inp","r"))
  116.     {
  117.     	freopen(name".inp","r",stdin);
  118.     	freopen(name".out","w",stdout);
  119.     }
  120.     cin >> n;
  121.     FOR(i,1,n) cin >> h[i];
  122.     // if (sub2::approved()) return sub2::solve(), time(), memory(), 0;
  123.     sub5::solve();
  124.     time();
  125.     memory();
  126.     return 0;
  127. }
  128. // ██░ ██  █    ██  ███▄    █   ▄████
  129. //▓██░ ██▒ ██  ▓██▒ ██ ▀█   █  ██▒ ▀█▒
  130. //▒██▀▀██░▓██  ▒██░▓██  ▀█ ██▒▒██░▄▄▄░
  131. //░▓█ ░██ ▓▓█  ░██░▓██▒  ▐▌██▒░▓█  ██▓
  132. //░▓█▒░██▓▒▒█████▓ ▒██░   ▓██░░▒▓███▀▒
  133. // ▒ ░░▒░▒░▒▓▒ ▒ ▒ ░ ▒░   ▒ ▒  ░▒   ▒
  134. // ▒ ░▒░ ░░░▒░ ░ ░ ░ ░░   ░ ▒░  ░   ░
  135. // ░  ░░ ░ ░░░ ░ ░    ░   ░ ░ ░ ░   ░
  136. // ░  ░  ░   ░              ░       ░
Success #stdin #stdout #stderr 0.01s 5320KB
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Standard input is empty
stdout
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Standard output is empty
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-------------Time:4.822ms.
76.2941 MB
https://ideone.com/REnLdJ
language:
C++14 (gcc 8.3)
created:
3 hours ago
visibility:
public

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