C/C++ Program to Count set bits in an integer Last Updated : 02 Jan, 2019 Improve Improve Like Article Like Save Share Report Write an efficient program to count number of 1s in binary representation of an integer. Examples : Input : n = 6 Output : 2 Binary representation of 6 is 110 and has 2 set bits Input : n = 13 Output : 3 Binary representation of 11 is 1101 and has 3 set bits Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution. 1. Simple Method Loop through all bits in an integer, check if a bit is set and if it is then increment the set bit count. See below program. C #include <stdio.h> /* Function to get no of set bits in binary representation of positive integer n */ unsigned int countSetBits(unsigned int n) { unsigned int count = 0; while (n) { count += n & 1; n >>= 1; } return count; } /* Program to test function countSetBits */ int main() { int i = 9; printf("%d", countSetBits(i)); return 0; } Output: 2 Recursive Approach : C++ // Cpp implementation of recursive // approach to find the number // of set bits in binary representation // of positive integer n #include <bits/stdc++.h> using namespace std; // recursive function to count set bits int countSetBits(int n) { // base case if (n == 0) return 0; else // if last bit set add 1 else add 0 return (n & 1) + countSetBits(n >> 1); } // driver code int main() { // get value from user int n = 9; // function calling cout << countSetBits(n); return 0; } // This code is contributed by Raj. Output: 2 Please refer complete article on Count set bits in an integer for more details! Like Article Suggest improvement Previous C Program for Find largest prime factor of a number Next C / C++ Program for Median of two sorted arrays of same size Share your thoughts in the comments Add Your Comment Please Login to comment... Similar Reads Program for conversion of 32 Bits Single Precision IEEE 754 Floating Point Representation C Program to Rotate bits of a number Lex Program to accept a valid integer and float value Program that allows integer input only C Program to Count Inversions in an array | Set 1 (Using Merge Sort) Sorting integer data from file and calculate execution time Frequency of an integer in the given array using Divide and Conquer Convert string to integer without using any in-built functions C Program for Disjoint Set (Or Union-Find) | Set 1 (Detect Cycle in an Undirected Graph) C Program to Check if count of divisors is even or odd Like GeeksforGeeks Article Tags : C Programs