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  1. #include <bits/stdc++.h> 
  2.  
  3. using namespace std;  
  4.  
  5. typedef long long ll;  
  6. typedef pair<int, int> ii;  
  7.  
  8. const int INF = 1e9;  
  9. const ll LINF = 1e18;  
  10.  
  11. const int N = 1e6 + 5;
  12.  
  13. int n;  
  14. int a[N];  
  15.  
  16. int sos[1 << 21][2];
  17.  
  18. void add(int mx[2], int x) {
  19. 	if (x > mx[0]) {
  20. 		mx[1] = mx[0];
  21. 		mx[0] = x; 
  22. 	}
  23. 	else {
  24. 		mx[1] = max(mx[1], x);
  25. 	}
  26. }
  27.  
  28. bool check(int ans) {
  29. 	for (int i = 1; i <= n; i++) {
  30. 		int x = (a[i] ^ ans) & ans; 
  31. 		if (sos[x][1] > i) return true; 
  32. 	}
  33. 	return false; 
  34. }
  35.  
  36. int main() {
  37. 	ios::sync_with_stdio(false); 
  38. 	cin.tie(nullptr); 	
  39. 	cin >> n; 
  40. 	for (int i = 1; i <= n; i++) cin >> a[i]; 
  41.  
  42. 	for (int i = 1; i <= n; i++) add(sos[a[i]], i);
  43.  
  44. 	for (int i = 0; i < 21; i++) {
  45. 		for (int mask = 0; mask < (1 << 21); mask++) {
  46. 			if (!(mask & (1 << i))) {
  47. 				add(sos[mask], sos[mask ^ (1 << i)][0]);
  48. 				add(sos[mask], sos[mask ^ (1 << i)][1]);
  49. 			}
  50. 		}
  51. 	}
  52.  
  53. 	int ans = 0;  
  54. 	for (int i = 20; i >= 0; i--) {
  55. 		if (check(ans | (1 << i))) ans |= (1 << i);
  56. 	}
  57.  
  58. 	cout << ans << '\n';
  59. }
Success #stdin #stdout 0.11s 21540KB
comments (?)
stdin 
3
2 4 6
stdout 
6
https://ideone.com/EXr8K8
language:
C++14 (gcc 8.3)
created:
11 days ago
visibility:
secret

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