Check if two numbers are bit rotations of each other or not

Given two positive integers x and y (0 < x, y < 2^32), check if one integer is obtained by rotating bits of the other.

Bit Rotation: A rotation (or circular shift) is an operation similar to a shift except that the bits that fall off at one end are put back to the other end.

Examples:

Input : a = 8, b = 1
Output : yes
Explanation : Representation of a = 8 : 0000 0000 0000 0000 0000 0000 0000 1000 ,Representation of b = 1 : 0000 0000 0000, 0000 0000 0000 0000 0001. If we rotate a by 3 units right we get b, hence answer is yes.

Input : a = 122, b = 2147483678
Output : yes
Explanation :Representation of a = 122        : 0000 0000 0000 0000 0000 0000 0111 1010,Representation of b = 2147483678 : 1000 0000 0000 0000 0000 0000 0001 1110, If we rotate a by 2 units right we get b, hence answer is yes.

Approach:

• Since total bits in which x or y can be represented is 32 since x, y > 0 and x, y < 2^32. 
• So we need to find all 32 possible rotations of x and compare them with y till x and y are not equal. 
• To do this we use a temporary variable x64 with 64 bits, which is result of the concatenation of x to x ie. x64 has the first 32 bits the same as bits of x and the last 32 bits are also the same as bits of x64.
• Then we keep on shifting x64 by 1 on the right side and compare the rightmost 32 bits of x64 with y. 
• In this way, we’ll be able to get all the possible bits combinations due to rotation.

Here is implementation of above algorithm.

C++

// C++ program to check if two numbers are bit rotations
// of each other.
#include <iostream>
using namespace std;

// function to check if  two numbers are equal
// after bit rotation
bool isRotation(unsigned int x, unsigned int y)
{
    // x64 has concatenation of x with itself.
    unsigned long long int x64 = x | ((unsigned long long int)x << 32);

    while (x64 >= y)
    {
        // comparing only last 32 bits
        if (unsigned(x64) == y)
            return true;

        // right shift by 1 unit
        x64 >>= 1;
    }
    return false;
}

// driver code to test above function
int main()
{
    unsigned int x = 122;
    unsigned int y = 2147483678;

    if (isRotation(x, y))
        cout << "yes" << endl;
    else
        cout << "no" << endl;

    return 0;
}

Java

// Java program to check if two numbers are bit rotations
// of each other.
class GFG {

// function to check if two numbers are equal
// after bit rotation
    static boolean isRotation(long x, long y) {
        // x64 has concatenation of x with itself.
        long x64 = x | (x << 32);

        while (x64 >= y) {
            // comparing only last 32 bits
            if (x64 == y) {
                return true;
            }

            // right shift by 1 unit
            x64 >>= 1;
        }
        return false;
    }

// driver code to test above function
    public static void main(String[] args) {
        long x = 122;
        long y = 2147483678L;

        if (isRotation(x, y) == false) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}

// This code is contributed by 29AjayKumar

Python3

# Python3 program to check if two
# numbers are bit rotations of each other.

# function to check if two numbers
# are equal after bit rotation
def isRotation(x, y) :

    # x64 has concatenation of x
    # with itself.
    x64 = x | (x << 32)

    while (x64 >= y) :

        # comparing only last 32 bits
        if ((x64) == y) :
            return True

        # right shift by 1 unit
        x64 >>= 1

    return False

# Driver Code
if __name__ == "__main__" :

    x = 122
    y = 2147483678

    if (isRotation(x, y) == False) :
        print("yes")
    else :
        print("no")

# This code is contributed by Ryuga

C#

// C# program to check if two numbers
// are bit rotations of each other.
using System;

class GFG
{

// function to check if two numbers
// are equal after bit rotation
static bool isRotation(long x, long y)
{
    // x64 has concatenation of
    // x with itself.
    long x64 = x | (x << 32);

    while (x64 >= y)
    {
        // comparing only last 32 bits
        if (x64 == y)
        {
            return true;
        }

        // right shift by 1 unit
        x64 >>= 1;
    }
    return false;
}

// Driver Code
public static void Main()
{
    long x = 122;
    long y = 2147483678L;

    if (isRotation(x, y) == false)
    {
        Console.Write("Yes");
    }
    else
    {
        Console.Write("No");
    }
}
}

// This code is contributed
// by 29AjayKumar

PHP

<?php
// PHP program to check if two
// numbers are bit rotations of
// each other.

// function to check if two
// numbers are equal after
// bit rotation
function isRotation($x, $y)
{
    // x64 has concatenation
    // of x with itself.
    $x64 = $x | ($x << 32);

    while ($x64 >= $y)
    {
        // comparing only last 32 bits
        if (($x64) == $y)
            return 1;

        // right shift by 1 unit
        $x64 >>= 1;
    }
    return -1;
}

// Driver Code
$x = 122;
$y = 2147483678;

if (isRotation($x, $y))
    echo "yes" ,"\n";
else
    echo "no" ,"\n";

// This code is contributed by aj_36
?>

Javascript

<script>

// javascript program to check if two numbers are bit rotations
// of each other.

// function to check if two numbers are equal
// after bit rotation
function isRotation(x, y)
{

    // x64 has concatenation of x with itself.
    var x64 = x | (x << 32);
    while (x64 >= y)
    {

        // comparing only last 32 bits
        if (x64 == y) {
            return true;
        }

        // right shift by 1 unit
        x64 >>= 1;
    }
    return false;
}

// driver code to test above function
var x = 122;
var y = 2147483678;

if (isRotation(x, y) == false) {
    document.write("Yes");
} else {
    document.write("No");
}

// This code is contributed by 29AjayKumar
</script>

Output

yes

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

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