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  1. //#pragma GCC optimize("O3")
  2. //#pragma GCC optimize("Ofast")
  3. //#pragma GCC optimize("unroll-loops")
  4. #include <bits/stdc++.h>
  5. using namespace std;
  6. #define ll long long
  7. #define db double
  8. #define is insert
  9. #define pb push_back
  10. #define pii pair<int, int>
  11. #define pll pair<long long, long long>
  12. #define X first
  13. #define Y second
  14. #define vi vector<int>
  15. #define vpi vector<pair<int, int>>
  16. #define msi multiset<int>
  17. #define int long long
  18. const int m97 = (int)1e9+7;
  19. const int m83 = 998244353;
  20. const int N = 1005;
  21. const int K = 30;
  22. const int inf = (int)1e18;
  23.  
  24. //mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
  25.  
  26. int n, m;
  27. int a[N][N];
  28. int h[N], l[N], r[N];
  29.  
  30. void solve(){
  31. 	cin >> n >> m;
  32. 	for(int i=1; i<=n; i++){
  33. 		for(int j=1; j<=m; j++){
  34. 			cin >> a[i][j];
  35. 		}
  36. 	}
  37. 	if(n <= 20){
  38. 		int mx = 0;
  39. 		for(int i1=1; i1<=n; i1++){
  40. 			for(int j1=1; j1<=m; j1++){
  41. 				for(int i2 = 1; i2 <= i1; i2++){
  42. 					for(int j2 = 1; j2 <= j1; j2++){
  43. 						bool ok = 1;
  44. 						int tar = a[i1][j1];
  45. 						for(int curi = i2; curi <= i1; curi++){
  46. 							for(int curj = j2; curj <= j1; curj++){
  47. 								ok &= (a[curi][curj] == tar);
  48. 							}
  49. 						}
  50. 						if(ok){
  51. 							mx = max((i1 - i2 + 1 + j1 - j2 + 1) * 2, mx);
  52. 						}
  53. 					}
  54. 				}
  55. 			}
  56. 		}
  57. 		cout << mx << "\n";
  58. 	}
  59. 	else{
  60. 		int mx = 0;
  61. 		for(int cur = 0; cur <= 9; cur++){
  62. 			fill(h + 1, h + m + 1, 0);
  63. 			fill(l + 1, l + m + 1, 1);
  64. 			fill(r + 1, r + m + 1, m + 1);
  65. 			for(int i=1; i <=n; i++){
  66. 				for(int j=1; j<=m; j++){
  67. 					h[j] = (a[i][j] == cur ? h[j] + 1 : 0);
  68. 				}
  69. 				int cl = 1;
  70. 				for(int j=1; j<=m; j++){
  71. 					if(a[i][j] == cur){
  72. 						l[j] = max(l[j], cl);
  73. 					}	
  74. 					else{
  75. 						l[j] = 1;
  76. 						cl = j + 1;
  77. 					}
  78. 				}
  79. 				int cr = m + 1;
  80. 				for(int j=m; j>=1; j--){
  81. 					if(a[i][j] == cur){
  82. 						r[j] = min(r[j], cr);
  83. 					}
  84. 					else{
  85. 						r[j] = m + 1;
  86. 						cr = j;
  87. 					}
  88. 				}
  89. 				for(int j=1; j <= m; j++){
  90. 					int ch = h[j];
  91. 					int cw = r[j] - l[j];
  92. 					if(ch > 0 && cw > 0){
  93. 						mx = max(mx, (ch + cw) * 2);
  94. 					}
  95. 				}
  96. 			}
  97. 		}
  98. 		cout << mx;
  99. 	}
  100. }
  101.  
  102. signed main(){
  103. 	freopen("FLATLAND.INP", "r", stdin);
  104.     freopen("FLATLAND.OUT", "w", stdout);
  105.     ios::sync_with_stdio(0);
  106.     cin.tie(0); cout.tie(0);
  107.     int tt = 1; //cin >> tt;
  108.     while(tt--){
  109.     	solve();
  110. 	}
  111. }
  112.  
  113. /*
  114. sample
  115.  
  116.  
  117.  
  118. */
  119.  
Success #stdin #stdout 0.01s 5328KB
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https://ideone.com/GG4plN
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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