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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. #define print(a)         for(auto x : a) cout << x << " "; cout << endl
  6.  
  7.  
  8. const int M = 1000000007;
  9. const int N = 3e5+9;
  10. const int INF = 2e9+1;
  11. const int LINF = 2000000000000000001;
  12.  
  13. inline int power(int a, int b, int mod=M) {
  14.     int x = 1;
  15.     a %= mod;
  16.     while (b) {
  17.         if (b & 1) x = (x * a) % mod; 
  18.         a = (a * a) % mod;
  19.         b >>= 1;
  20.     }
  21.     return x;
  22. }
  23.  
  24.  
  25. //_ ***************************** START Below *******************************
  26.  
  27.  
  28.  
  29.  
  30. vector<int> a;
  31.  
  32. int consistency(int n){
  33.  
  34. 	if(n==1) return 0;
  35. 	if(n==2) return 1;
  36.  
  37. 	vector<vector<vector<int>>> dp(n, vector<vector<int>>(n, vector<int>(3, 0)));
  38.  
  39. 	int s1 = a[0] + a[1];
  40. 	int s2 = a[0] + a[n-1];
  41. 	int s3 = a[n-2] + a[n-1];
  42.  
  43. 	int target[3] = {s1, s2, s3};
  44.  
  45. 	for(int k=0; k<3; k++){
  46.  
  47. 	    for(int gap=0; gap<n; gap++){
  48. 			for(int i=0, j=gap; j<n; i++, j++){
  49. 				if(gap == 0){
  50. 					dp[i][j][k] = 0;
  51. 				}
  52. 				else if(gap == 1){
  53.  
  54. 					if(a[i] + a[i+1] == target[k]){
  55. 						dp[i][j][k] = 1;
  56. 					}
  57. 				}
  58. 				else{
  59.  
  60. 					if(a[i] + a[i+1] == target[k]){
  61. 						dp[i][j][k] = max( dp[i][j][k] , 1 + dp[i+2][j][k] );
  62. 					}
  63. 					if(a[i] + a[j] == target[k]){
  64. 						dp[i][j][k] = max( dp[i][j][k] , 1 + dp[i+1][j-1][k] );
  65. 					}
  66. 					if(a[j-1] + a[j] == target[k]){
  67. 						dp[i][j][k] = max( dp[i][j][k] , 1 + dp[i][j-2][k] );
  68. 					}
  69. 				}
  70. 			}
  71. 		}
  72. 	}
  73.  
  74. 	return max({dp[0][n-1][0], dp[0][n-1][1], dp[0][n-1][2]});
  75. }
  76.  
  77.  
  78.  
  79.  
  80.  
  81.  
  82.  
  83.  
  84.  
  85.  
  86.  
  87.  
  88.  
  89.  
  90.  
  91. int practice(int n){
  92.  
  93.  
  94.     return 0;
  95. }
  96.  
  97.  
  98.  
  99.  
  100.  
  101. void solve() {
  102.  
  103.     int n;
  104.     cin>> n;
  105.  
  106.     a.resize(n);
  107.     for(int i=0; i<n; i++) cin >> a[i];
  108.  
  109.     cout << consistency(n) << endl;
  110.  
  111.  
  112. }
  113.  
  114.  
  115.  
  116.  
  117.  
  118. int32_t main() {
  119.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  120.  
  121.     int t = 1;
  122.     // cin >> t;
  123.     while (t--) {
  124.         solve();
  125.     }
  126.  
  127.     return 0;
  128. }
Success #stdin #stdout 0s 5276KB
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https://ideone.com/f8tXNy
language:
C++14 (gcc 8.3)
created:
11 hours ago
visibility:
public

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