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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. bool consistency1(int n){
  33.  
  34. 	vector<bool> dp(n+1, 0);
  35. 	dp[0] = 1;
  36. 	if(a[0] == 0) dp[1] = 1;
  37.  
  38. 	for(int i=2; i<=n; i++){
  39.  
  40. 		int j = i-1;
  41. 		while(j>=0){
  42.  
  43. 			if(a[j]+1 == i-j){
  44. 				dp[i] = dp[i] || dp[j];
  45. 			}
  46.  
  47. 			if(dp[i]) break;
  48. 			j--;
  49. 		}
  50.  
  51. 	}
  52.  
  53. 	return dp[n];
  54. }
  55.  
  56.  
  57.  
  58.  
  59.  
  60. bool consistency2(int n){
  61.  
  62. 	vector<bool> dp(n+1, 0);
  63. 	dp[0] = 1;
  64.  
  65. 	unordered_map<int,bool> mp = {{1+a[0] , dp[0]}};
  66.  
  67. 	for(int i=1; i<=n; i++){
  68. 		if(dp[i-1] == 1) mp[a[i-1]+i] = dp[i-1];
  69.  
  70. 		if(mp.count(i)){
  71. 			dp[i] = mp[i];
  72. 		}
  73.  
  74.  
  75. 	}
  76.  
  77. 	return dp[n];
  78. }
  79.  
  80.  
  81.  
  82. //* Approach 2 : Pick / Not Pick 
  83.  
  84. bool consistency3(int n){
  85.  
  86. 	vector<bool> dp(n+1, 0);
  87. 	dp[n] = 1;
  88.  
  89. 	for(int i=n-1; i>=0; i--){
  90.  
  91. 		dp[i] = dp[i+1];
  92. 		if(a[i]+i+1<=n) dp[i] = dp[i] || dp[a[i]+i+1];
  93.  
  94. 	}
  95.  
  96. 	return dp[0];
  97. }
  98.  
  99.  
  100.  
  101.  
  102.  
  103.  
  104.  
  105.  
  106.  
  107.  
  108.  
  109.  
  110. int practice(int n){
  111.  
  112.  
  113.     return 0;
  114. }
  115.  
  116.  
  117.  
  118.  
  119.  
  120. void solve() {
  121.  
  122.     int n;
  123.     cin>> n;
  124.  
  125.     a.resize(n);
  126.     for(int i=0; i<n; i++) cin >> a[i];
  127.  
  128.     cout << consistency1(n) << " " << consistency2(n) << " " << consistency3(n) << endl;
  129.  
  130.  
  131. }
  132.  
  133.  
  134.  
  135.  
  136.  
  137. int32_t main() {
  138.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  139.  
  140.     int t = 1;
  141.     // cin >> t;
  142.     while (t--) {
  143.         solve();
  144.     }
  145.  
  146.     return 0;
  147. }
Success #stdin #stdout 0s 5324KB
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https://ideone.com/SklmXl
language:
C++14 (gcc 8.3)
created:
9 hours ago
visibility:
public

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