Maximum Bitwise AND pair from given range in C++

Problem statement

Given a range [L, R], the task is to find a pair (X, Y) such that L ≤ X < Y ≤ R and X & Y is maximum among all the possible pairs then print the bitwise AND of the found pair.

Example

If L = 1 and R = 10 then maximum bitwise AND value is 8 which can be formed as follows −

1000 # Binary representation of 8
Bitwise AND
1001 # Binary representation of 9
----
1000 # Final result

Algorithm

Iterate from L to R and check the bitwise AND for every possible pair and print the maximum value in the ends

Example

Let us now see an example −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
int getMaxBitwiseAndValue(int L, int R) {
   int maxValue = L & R;
   for (int i = L; i < R; ++i) {
      for (int j = i + 1; j <= R; ++j) {
         maxValue = max(maxValue, (i & j));
      }
   }
   return maxValue;
}
int main() {
   int L = 1, R = 10;
   cout << "Maximum value = " << getMaxBitwiseAndValue(L, R) << endl;
   return 0;
}

Output

Maximum value = 8