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Comparing leading zeros in binary representations of two numbers
  • Last Updated : 28 Apr, 2021

Given two integer numbers x and y. Compare and print which one of them has more leading zeros using Bitwise operation. If both the no. have the same no. of leading zeros, print “Equal”.
Note:- A leading zero is any 0 digit that comes before the first nonzero digit in the binary notation of the number.
Examples: 
 

Input : 10, 16
Output :10
Explanation: If we represent the no.s using 8 bit only then 
Binary(10) = 00001010
Binary(16) = 00010000
Clearly, 10 has 4 leading zeros and 16 has 3 leading zeros

Input : 10, 12
Output : Equal
Binary(10) = 00001010
Binary(12) = 00001100
Both have equal no. of leading zeros.

 

Solution 1: The Naive approach is to first find the binary representation of the numbers and then count the no. of leading zeros.
Solution 2: Find largest power of twos smaller than given numbers, and compare these powers of twos to decide answer.
Solution 3: An efficient approach is to bitwise XOR and AND operators.
 

Case 1: If both have same no. of leading zeros then (x^y) <= (x & y) because same number of leading 0s would cause a 1 at higher position in x & y.
Case 2 : If we do negation of y and do bitwise AND with x, we get a one at higher position than in y when y has more number of leading 0s.
Case 3: Else x has more leading zeros

 



C++




// CPP program to find the number with more
// leading zeroes.
#include <bits/stdc++.h>
using namespace std;
 
// Function to compare the no. of leading zeros
void LeadingZeros(int x, int y)
{
    // if both have same no. of leading zeros
    if ((x ^ y) <= (x & y))
        cout << "\nEqual";
 
    // if y has more leading zeros
    else if ((x & (~y)) > y)
        cout << y;
 
    else
        cout << x;
}
 
// Main Function
int main()
{
    int x = 10, y = 16;
    LeadingZeros(x, y);
    return 0;
}

Java




// Java program to find the number
// with more leading zeroes.
class GFG
{
// Function to compare the no.
// of leading zeros
static void LeadingZeros(int x, int y)
{
    // if both have same no. of
    // leading zeros
    if ((x ^ y) <= (x & y))
        System.out.print("\nEqual");
 
    // if y has more leading zeros
    else if ((x & (~y)) > y)
        System.out.print(y);
 
    else
        System.out.print(x);
}
 
// Driver Code
public static void main (String[] args)
{
    int x = 10, y = 16;
    LeadingZeros(x, y);
}
}
 
// This code is contributed by Smitha

Python3




# Python 3 program to find the number
# with more leading zeroes.
 
# Function to compare the no. of
# leading zeros
def LeadingZeros(x, y):
     
    # if both have same no. of
    # leading zeros
    if ((x ^ y) <= (x & y)):
        print("Equal")
 
    # if y has more leading zeros
    elif ((x & (~y)) > y) :
        print(y)
 
    else:
        print(x)
 
# Driver Code
if __name__ == '__main__':
    x = 10
    y = 16
    LeadingZeros(x, y)
 
# This code is contributed
# by Surendra_Gangwar

C#




// C# program to find the number
// with more leading zeroes.
using System;
 
class GFG
{
// Function to compare the no.
// of leading zeros
static void LeadingZeros(int x, int y)
{
    // if both have same no. of
    // leading zeros
    if ((x ^ y) <= (x & y))
        Console.WriteLine("\nEqual");
 
    // if y has more leading zeros
    else if ((x & (~y)) > y)
        Console.WriteLine(y);
 
    else
        Console.WriteLine(x);
}
 
// Driver Code
static public void Main ()
{
    int x = 10, y = 16;
    LeadingZeros(x, y);
}
}
 
// This code is contributed by ajit

PHP




<?php
// PHP program to find the number
// with more leading zeroes.
 
// Function to compare the no.
// of leading zeros
function LeadingZeros($x, $y)
{
    // if both have same no. of
    // leading zeros
    if (($x ^ $y) <= ($x & $y))
        echo "\nEqual";
 
    // if y has more leading zeros
    else if (($x & (~$y)) > $y)
        echo $y;
 
    else
        echo $x;
}
 
// Driver Code
$x = 10;
$y = 16;
LeadingZeros($x, $y);
     
// This code is contributed by ajit
?>

Javascript




<script>
 
// Javascript program to find the number with more
// leading zeroes.
 
// Function to compare the no. of leading zeros
function LeadingZeros(x, y)
{
    // if both have same no. of leading zeros
    if ((x ^ y) <= (x & y))
        document.write("<br>Equal");
 
    // if y has more leading zeros
    else if ((x & (~y)) > y)
        document.write(y);
 
    else
        document.write(x);
}
 
// Main Function
    let x = 10, y = 16;
    LeadingZeros(x, y);
 
</script>
Output: 
10

 

Time Complexity: O(1) 
Space Complexity: O(1)
 

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