C++ Program to Count 1's in a sorted binary array

C/C++ Program to Count set bits in an integer

Last Updated : 02 Jan, 2019

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

setbit

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:

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:

Please refer complete article on Count set bits in an integer for more details!

C++ Program to Count 1's in a sorted binary array

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