Given two numbers ‘a’ and b’. Write a program to count number of bits needed to be flipped to convert ‘a’ to ‘b’.
Example :
Input : a = 10, b = 20 Output : 4 Binary representation of a is 00001010 Binary representation of b is 00010100 We need to flip highlighted four bits in a to make it b. Input : a = 7, b = 10 Output : 3 Binary representation of a is 00000111 Binary representation of b is 00001010 We need to flip highlighted three bits in a to make it b.
1. Calculate XOR of A and B.
a_xor_b = A ^ B
2. Count the set bits in the above
calculated XOR result.
countSetBits(a_xor_b)
XOR of two number will have set bits only at those places where A differs from B.
C++
// Count number of bits to be flipped // to convert A into B #include <iostream> using namespace std; // Function that count set bits int countSetBits(int n) { int count = 0; while (n > 0) { count++; n &= (n-1); } return count; } // Function that return count of // flipped number int FlippedCount(int a, int b) { // Return count of set bits in // a XOR b return countSetBits(a^b); } // Driver code int main() { int a = 10; int b = 20; cout << FlippedCount(a, b)<<endl; return 0; } |
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Java
// Count number of bits to be flipped // to convert A into B import java.util.*; class Count { // Function that count set bits public static int countSetBits(int n) { int count = 0; while (n != 0) { count++; n &=(n-1); } return count; } // Function that return count of // flipped number public static int FlippedCount(int a, int b) { // Return count of set bits in // a XOR b return countSetBits(a ^ b); } // Driver code public static void main(String[] args) { int a = 10; int b = 20; System.out.print(FlippedCount(a, b)); } } // This code is contributed by rishabh_jain |
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Python3
# Count number of bits to be flipped # to convert A into B # Function that count set bits def countSetBits( n ): count = 0 while n: count += 1 n &= (n-1) return count # Function that return count of # flipped number def FlippedCount(a , b): # Return count of set bits in # a XOR b return countSetBits(a^b) # Driver code a = 10b = 20print(FlippedCount(a, b)) # This code is contributed by "Sharad_Bhardwaj". |
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C#
// Count number of bits to be // flipped to convert A into B using System; class Count { // Function that count set bits public static int countSetBits(int n) { int count = 0; while (n != 0) { count++; n &= (n-1); } return count; } // Function that return // count of flipped number public static int FlippedCount(int a, int b) { // Return count of set // bits in a XOR b return countSetBits(a ^ b); } // Driver code public static void Main() { int a = 10; int b = 20; Console.WriteLine(FlippedCount(a, b)); } } // This code is contributed by vt_m. |
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PHP
<?php // Count number of bits to be // flipped to convert A into B // Function that count set bits function countSetBits($n) { $count = 0; while($n) { $count += 1; $n &= (n-1); } return $count; } // Function that return // count of flipped number function FlippedCount($a, $b) { // Return count of set // bits in a XOR b return countSetBits($a ^ $b); } // Driver code $a = 10; $b = 20; echo FlippedCount($a, $b); // This code is contributed by mits ?> |
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Output :
4
Thanks to Sahil Rajput for providing above implementation.
To get the set bit count please see this post: Count set bits in an integer
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