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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define int long long
  4. #define vi vector<int>
  5. #define zip(i,a,b) for(int i=a;i<b;i++)
  6. #define rzip(i,a,b) for(int i=a;i>=b;i--)
  7. #define test int t;cin>>t; while(t--)
  8. #define en '\n'
  9.  
  10.  
  11. int maximumXOR(int n, int l, int r)
  12. {
  13. 	int x = 0;
  14. 	for (int i = log2(r); i >= 0; --i)
  15. 	{
  16. 		if (n & (1 << i))
  17. 		{
  18. 			if ((x > r) || (x + (1 << i) - 1 < l))
  19. 				x ^= (1 << i);
  20. 		}
  21. 		else
  22. 		{
  23. 			if ((x ^ (1 << i)) <= r)
  24. 				x ^= (1 << i);
  25. 		}
  26. 	}
  27. 	return n ^ x;
  28. }
  29.  
  30.  
  31.  
  32. int32_t main()
  33. {
  34.    // i have already declared int as long long
  35. 	int n;
  36. 	cin >> n;
  37. 	int a[n];
  38. 	zip(i, 0, n)
  39. 	{
  40. 		cin >> a[i];
  41. 	}
  42. 	sort(a, a + n);
  43. 	vi pre(n);
  44. 	vi suff(n);
  45. 	pre[0] = a[0];
  46. 	zip(i, 1, n)
  47. 	{
  48. 		pre[i] = (pre[i - 1] ^ a[i]);
  49. 	}
  50. 	suff[n - 1] = a[n - 1];
  51. 	rzip(i, n - 2, 0)
  52. 	{
  53. 		suff[i] = (suff[i + 1] ^ a[i]);
  54. 	}
  55. 	int ans = suff[0];
  56. 	zip(i, 0, n - 2)
  57. 	{
  58. 		// as we can check only one element first take xor of pre[i]^suf[i+2] and change value accordingly.
  59. 		int x = pre[i];
  60. 		int y = suff[i + 2];
  61. 		x = (x ^ suff[i + 2]);
  62. 		int p = a[i + 1];
  63. 		ans = max(ans, maximumXOR(x, 0, p));
  64. 	}
  65. 	if (n > 1)
  66. 	{
  67. 		ans = max(ans, maximumXOR(suff[1], 0, a[0]));
  68. 		ans = max(ans, maximumXOR(pre[n - 2], 0, a[n - 1]));
  69. 	}
  70. 	cout << ans << en;
  71.  
  72. 	return 0;
  73. }
  74.  
  75.  
  76.  
Runtime error #stdin #stdout 0s 4308KB
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/w4ubj0
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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