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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	int arr[]= {10,5,2,7,1,9};
  6. 	int n=sizeof(arr)/sizeof(arr[0]);
  7. 	int k=15;
  8. 	int maxLength=0;
  9. 	vector<int> prefixXor(n);
  10. 	prefixXor[0]=arr[0];
  11. 	for(int i=1;i<n;i++)
  12. 		prefixXor[i]=prefixXor[i-1]^arr[i];
  13. 	unordered_map<int, int> mp;
  14. 	mp[0]=-1;
  15. 	for(int j=0;j<n;j++){
  16. 		int toFind=prefixXor[j]^k;	
  17. 		if(mp.find(prefixXor[j])!=mp.end()){
  18. 			int i=mp[toFind]+1;    //note that the actual subarray with xor k is from i+1 to j
  19.                                                        	             //bcoz we look for P(i-1) s.t P(i-1)^XOR(i…j)=P(j)
  20. 						//so P(i-1)^k=p(j) as we have assumed XOR(i…j) = k 
  21. 			int length=j-i+1;
  22. 			maxLength=max(length, maxLength);
  23. 		}
  24. 		if(mp.find(prefixXor[j])==mp.end())
  25. 			mp[prefixXor[j]]=j;
  26. 	}
  27. 	cout<<maxLength;
  28. 	return 0;
  29. }
  30.  
Success #stdin #stdout 0s 5276KB
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https://ideone.com/0TwoWx
language:
C++ (gcc 8.3)
created:
2 hours ago
visibility:
public

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