Next higher number with same number of set bits in C++

We are given a number n, we have to find the number that is greater than n with same number of set bits as n in its binary representation.

The digit 1 in the binary representation is called set bit.

Let's see an example.

Input

124

Output

143

Algorithm

• Initialise the number n.

• Write a function get the count of number of set bits.

• Initialise the iterative variable with n + 1.

• Write an infinite loop.

  • Check for the number of set bits for numbers equal to the number of set bits of n.

  • Return the number when you find it.

  • Increment the number.

Implementation

Following is the implementation of the above algorithm in C++

#include <bits/stdc++.h>
using namespace std;
int getSetBitsCount(int n) {
   int count = 0;
   while (n) {
      if (n % 2 == 1) {
         count += 1;
      }
      n /= 2;
   }
   return count;
}
int getNextGreaterElementWithSameSetBits(int n) {
   int setBitsCount = getSetBitsCount(n);
   int i = n + 1;
   while (true) {
      if (setBitsCount == getSetBitsCount(i)) {
         return i;
      }
      i += 1;
   }
}
int main() {
   int n = 124;
   cout << getNextGreaterElementWithSameSetBits(n) << endl;
   return 0;
}

Output

If you run the above code, then you will get the following result.

143