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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define int long long
  4. #define fr(i,a,b) for(int i=a;i<=b;i++)
  5. #define sz(x) (int)(x.size())
  6. #define vi vector<int>
  7. #define all(v) (v).begin(),(v).end()
  8. #define pb push_back
  9. int binpow(int a, int b) 
  10. {
  11.     int res = 1;
  12.     while(b>0) 
  13.     {
  14.         if(b&1)
  15.         res=res*a;
  16.         a=a*a;
  17.         b>>=1;
  18.     }
  19.     return res;
  20. }
  21. int32_t main()
  22. {
  23.   	int n;
  24.     cin>>n;
  25.     int arr[n];
  26.     fr(i,0,n-1)
  27.     cin>>arr[i];
  28.   	int c=0;
  29.   	vi vect;
  30.   	for(int bit=0;bit<64;bit++)
  31.   	{
  32.   		c=0;
  33.   		for(int i=0;i<n;i++)
  34.   		{
  35.   			if(arr[i]&(1LL<<bit))
  36.   				c++;
  37.   		}
  38.   		if(c%2==0&&c>=2)
  39.   		{
  40.   			vect.pb(bit);
  41.   		}
  42.   	}
  43.   	int x=0;
  44.   	fr(i,0,n-1)
  45.   	{
  46.   		x^=arr[i];
  47.   	}
  48.   	if(sz(vect)==0)
  49.   	{
  50.   		cout<<x<<endl;
  51.   		return 0;
  52.   	}
  53.   	vi v(n,0);
  54.   	reverse(all(vect));
  55.   	for(int i=0;i<n;i++)
  56.   	{
  57.   		int j=0;
  58.   		for(;j<sz(vect);j++)
  59.   		{
  60.   			if(arr[i]&(1LL<<vect[j]))
  61.   			{
  62.   				break;//positon of the first set bit
  63.   			}
  64.   		}
  65.   		for(;j<sz(vect);j++)
  66.   		{
  67.   			v[i]+=binpow(2,vect[j]);
  68.   		}
  69.   	}
  70.   	x+=*max_element(all(v));
  71.   	cout<<x<<endl;
  72. return 0;
  73. }
Runtime error #stdin #stdout 0s 4452KB
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https://ideone.com/USlMYJ
language:
C++14 (gcc 8.3)
created:
3 years ago
visibility:
secret

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