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Maximum XOR value of a pair from a range in C++
Problem statement
Given a range [L, R], we need to find two integers in this range such that their XOR is maximum among all possible choices of two integers
If the given range is L = 1 and R = 21 then the output will be 31 as − 31 is XOR of 15 and 16 and it is maximum within range.
Algorithm
1. Calculate the (L^R) value 2. From most significant bit of this value add all 1s to get the final result
Example
#include <bits/stdc++.h> using namespace std; int getMaxXOR(int L, int R){ int LXR = L ^ R; int msbPos = 0; while (LXR) { msbPos++; LXR >>= 1; } int maxXOR = 0; int two = 1; while (msbPos--) { maxXOR += two; two <<= 1; } return maxXOR; } int main(){ int L = 1; int R = 21; cout << "Result = " << getMaxXOR(L, R) << endl; return 0; }
Output
When you compile and execute the above program. It generates the following output −
Result = 31
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