Count number of bits changed after adding 1 to given N

Given an integer N. The task is to find the number of bits changed after adding 1 to the given number.

Examples:

Input : N = 5
Output : 2
After adding 1 to 5 it becomes 6.
Binary representation of 5 is 101.
Binary representation of 6 is 110.
So, no. of bits changed is 2.

Input : N = 1
Output : 2


There are three approaches to find the number of changed bits in the result obtained after adding 1 to the given value N:

  • Approach 1: Add 1 to given integer and compare the bits of N and the result obtained after addition and count the number of unmatched bit.
  • Approach 2: In case if 1 is added to N, then the total number of bits changed is defined by the position of 1st Zero from right i.e. LSB as zero. In the case, 1 is added to 1 then it got changed and pass a carry 1 to its next bit but if 1 is added to 0 only 0 changes to 1 and no further carry is passed.
  • Approach 3: For finding number of changed bits when 1 is added to a given number take XOR of n and n+1 and calculate the number of set bits in the resultant XOR value.

Below is the implementation of the Approach 3:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to find the number
// of changed bit
#include <bits/stdc++.h>
using namespace std;
  
// Function to find number of changed bit
int findChangedBit(int n)
{
    // Calculate xor of n and n+1
    int XOR = n ^ (n + 1);
  
    // Count set bits in xor value
    int result = __builtin_popcount(XOR);
  
    // Return the result
    return result;
}
  
// Driver function
int main()
{
    int n = 6;
    cout << findChangedBit(n) << endl;
  
    n = 7;
    cout << findChangedBit(n);
  
    return 0;
}

chevron_right


Python3

# Python 3 program to find the number
# of changed bit

# Function to find number of changed bit
def findChangedBit(n):

# Calculate xor of n and n+1
XOR = n ^ (n + 1)

# Count set bits in xor value
result = bin(XOR).count(“1”)

# Return the result
return result

# Driver Code
if __name__ == ‘__main__’:
n = 6
print(findChangedBit(n))

n = 7
print(findChangedBit(n))

# This code is contributed by
# Surendra_Gangwar

Output:

1
4


My Personal Notes arrow_drop_up

Discovering ways to develop a plane for soaring career goals

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : SURENDRA_GANGWAR



Article Tags :
Practice Tags :


Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.