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Count total unset bits in all the numbers from 1 to N

Last Updated : 12 Nov, 2021
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Given a positive integer N, the task is to count the total number of unset bits in the binary representation of all the numbers from 1 to N. Note that leading zeroes will not be counted as unset bits.
Examples: 
 

Input: N = 5 
Output:
 

IntegerBinary RepresentationCount of unset bits
110
2101
3110
41002
51011


0 + 1 + 0 + 2 + 1 = 4
Input: N = 14 
Output: 17 
 


 


Approach: 
 

  1. Iterate the loop from 1 to N.
  2. While number is greater than 0 divide it by 2 and check the remainder.
  3. If remainder is equal to 0 then increase the value of count by 1.


Below is the implementation of the above approach: 
 

C++
// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;

// Function to return the count of unset
// bits in the binary representation of
// all the numbers from 1 to n
int countUnsetBits(int n)
{

    // To store the count of unset bits
    int cnt = 0;

    // For every integer from the range [1, n]
    for (int i = 1; i <= n; i++) {

        // A copy of the current integer
        int temp = i;

        // Count of unset bits in
        // the current integer
        while (temp) {

            // If current bit is unset
            if (temp % 2 == 0)
                cnt++;

            temp = temp / 2;
        }
    }
    return cnt;
}

// Driver code
int main()
{
    int n = 5;

    cout << countUnsetBits(n);

    return 0;
}
Java
// Java implementation of the approach
class GFG
{

    // Function to return the count of unset
    // bits in the binary representation of
    // all the numbers from 1 to n
    static int countUnsetBits(int n)
    {

        // To store the count of unset bits
        int cnt = 0;

        // For every integer from the range [1, n]
        for (int i = 1; i <= n; i++) 
        {

            // A copy of the current integer
            int temp = i;

            // Count of unset bits in
            // the current integer
            while (temp > 0)
            {

                // If current bit is unset
                if (temp % 2 == 0)
                {
                    cnt = cnt + 1;
                }

                temp = temp / 2;
            }
        }
        return cnt;
    }

    // Driver code
    public static void main(String[] args) 
    {
        int n = 5;
        System.out.println(countUnsetBits(n));
    }
}

// This code is contributed by 29AjayKumar
Python3
# Python3 implementation of the approach 

# Function to return the count of unset 
# bits in the binary representation of 
# all the numbers from 1 to n 
def countUnsetBits(n) : 

    # To store the count of unset bits 
    cnt = 0; 

    # For every integer from the range [1, n] 
    for i in range(1, n + 1) :
        
        # A copy of the current integer 
        temp = i; 

        # Count of unset bits in 
        # the current integer 
        while (temp) :

            # If current bit is unset 
            if (temp % 2 == 0) :
                cnt += 1; 

            temp = temp // 2; 

    return cnt; 

# Driver code 
if __name__ == "__main__" : 

    n = 5; 

    print(countUnsetBits(n)); 
    
# This code is contributed by AnkitRai01
C#
// C# implementation of the approach
using System;

class GFG
{ 

    // Function to return the count of unset
    // bits in the binary representation of
    // all the numbers from 1 to n
    static int countUnsetBits(int n)
    {
    
        // To store the count of unset bits
        int cnt = 0;
    
        // For every integer from the range [1, n]
        for (int i = 1; i <= n; i++) 
        {
    
            // A copy of the current integer
            int temp = i;
    
            // Count of unset bits in
            // the current integer
            while (temp > 0) 
            {
    
                // If current bit is unset
                if (temp % 2 == 0)
                    cnt = cnt + 1;
    
                temp = temp / 2;
            }
        }
        return cnt;
    }

    // Driver code
    public static void Main() 
    {
        int n = 5;
        Console.Write(countUnsetBits(n)); 
    } 
}

// This code is contributed by Sanjit_Prasad
JavaScript
<script>

// Javascript implementation of the approach

// Function to return the count of unset
// bits in the binary representation of
// all the numbers from 1 to n
function countUnsetBits(n)
{

    // To store the count of unset bits
    var cnt = 0;

    // For every integer from the range [1, n]
    for (var i = 1; i <= n; i++) {

        // A copy of the current integer
        var temp = i;
        
        // Count of unset bits in
        // the current integer
        while (temp) {

            // If current bit is unset
            if (temp % 2 == 0)
                cnt++;

            temp = parseInt(temp / 2);
        }
    }
    return cnt;
}

// Driver code
var n = 5;
document.write( countUnsetBits(n));

</script>

Output: 
4

 

Time Complexity: O(n * log n)

Auxiliary Space: O(1)


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