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Set bits in N equals to M in the given range.

  • Difficulty Level : Medium
  • Last Updated : 29 Jun, 2021

You are given two 32-bit numbers, N and M, and two bit positions, i and j. Write a method to set all bits between i and j in N equal to M (e.g., M becomes a substring of N located at i and starting at j).
Examples : 
 

Input : N = 1, M = 2, i = 2, j = 4
Output: 9
N = 00000001(Considering 8 bits only)
M = 10 (Binary of 2) For more indexes,
leading zeroes will be considered.
Now set 3 bits from ith index to j in 
the N as in the M.
Bits:-    0 0 0 (0  1  0) 0 1 = 9
Indexes:- 7 6 5  4  3  2  1 0
From index 2 to 4, bits are set according 
to the M.

Asked in : Adobe
 

A simple solution is to traverse all bits in N from 0 to 31 and set the bits equals to M in the range from i to j.
An efficient solution is to do following steps.
 

  1. Set all the bits after j in a number.
  2. Set all the bits before i in a number.
  3. Then perform Bitwise Or on both then we get the number with all the bits set except from i to j.
  4. Perform Bitwise And with the given N as to set the bits according to the N.
  5. Then shift M into the correct position i.e. in the range of i to j.
  6. And at the last perform Bitwise Or on (Shifted M and the N modified in 4th step).
  7. The result will be N with M as substring from ith to jth bits

 

C++




// C++ program for above implementation
#include <iostream>
using namespace std;
 
// Function to set the bits
int setBits(int n, int m, int i, int j)
{
    // number with all 1's
    int allOnes = ~0;
 
    // Set all the bits in the left of j
    int left = allOnes << (j + 1);
 
    // Set all the bits in the right of j
    int right = ((1 << i) - 1);
 
    // Do Bitwsie OR to get all the bits
    // set except in the range from i to j
    int mask = left | right;
 
    // clear bits j through i
    int masked_n = n & mask;
 
    // move m into the correct position
    int m_shifted = m << i;
 
    // return the Bitwise OR of masked_n
    // and shifted_m
    return (masked_n | m_shifted);
}
 
// Drivers program
int main()
{
    int n = 2, m = 4;
    int i = 2, j = 4;
    cout << setBits(n, m, i, j);
    return 0;
}

Java




// Java Program
public class GFG
{
    // Function to set the bits
    static int setBits(int n, int m, int  i, int j)
    {
         
        // number with all 1's
        int  allOnes = ~0;
         
        // Set all the bits in the left of j
        int left = allOnes << (j + 1);
         
        // Set all the bits in the right of j
        int right = ((1 << i) - 1);
         
        // Do Bitwise OR to get all the bits
        // set except in the range from i to j
        int mask = left | right;
         
        // clear bits j through i
        int masked_n = n & mask;
         
        // move m into the correct position
        int m_shifted = m << i;
         
        // return the Bitwise OR of masked_n
        // and shifted_m
        return (masked_n | m_shifted);
    }
     
    // Driver Program to test above function
    public static void main(String[] args)
    {
        int n = 2, m = 4;
        int i = 2, j = 4;
        System.out.println(setBits(n, m, i, j));
    }
}
// This code is contributed by Sumit Ghosh

Python




# Python program for above implementation
 
# Function to set the bits
def setBits(n, m, i, j):
 
    # number with all 1's
    allOnes = not 0
  
    # Set all the bits in the left of j
    left = allOnes << (j + 1)
  
    # Set all the bits in the right of j
    right = ((1 << i) - 1)
  
    # Do Bitwsie OR to get all the bits
    # set except in the range from i to j
    mask = left | right
  
    # clear bits j through i
    masked_n = n & mask
  
    # move m into the correct position
    m_shifted = m << i
  
    # return the Bitwise OR of masked_n
    # and shifted_m
    return (masked_n | m_shifted)
  
# Drivers program
n, m = 2, 4
i, j = 2, 4
print setBits(n, m, i, j)
 
# This code is submitted by Sachin Bisht

C#




// C# Program for above implementation
using System;
 
public class GFG {
     
    // Function to set the bits
    static int setBits(int n, int m, int  i, int j)
    {
          
        // number with all 1's
        int  allOnes = ~0;
          
        // Set all the bits in the left of j
        int left = allOnes << (j + 1);
          
        // Set all the bits in the right of j
        int right = ((1 << i) - 1);
          
        // Do Bitwise OR to get all the bits
        // set except in the range from i to j
        int mask = left | right;
          
        // clear bits j through i
        int masked_n = n & mask;
          
        // move m into the correct position
        int m_shifted = m << i;
          
        // return the Bitwise OR of masked_n
        // and shifted_m
        return (masked_n | m_shifted);
    }
      
    // Driver Program to test above function
    public static void Main()
    {
        int n = 2, m = 4;
        int i = 2, j = 4;
         
        Console.WriteLine(setBits(n, m, i, j));
    }
}
 
// This code is contributed by Anant Agarwal.

PHP




<?php
// PHP program for above implementation
 
// Function to set the bits
function setBits($n, $m, $i, $j)
{
    // number with all 1's
    $allOnes = ~0;
 
    // Set all the bits
    // in the left of j
    $left = $allOnes << ($j + 1);
 
    // Set all the bits
    // in the right of j
    $right = ((1 << $i) - 1);
 
    // Do Bitwsie OR to get all
    // the bits set except in
    // the range from i to j
    $mask = $left | $right;
 
    // clear bits j through i
    $masked_n = $n & $mask;
 
    // move m into the
    // correct position
    $m_shifted = $m << $i;
 
    // return the Bitwise OR
    // of masked_n and shifted_m
    return ($masked_n | $m_shifted);
}
 
// Driver Code
$n = 2; $m = 4;
$i = 2; $j = 4;
echo setBits($n, $m, $i, $j);
 
// This code is contributed by ajit
?>

Javascript




<script>
    // Javascript Program for above implementation
     
    // Function to set the bits
    function setBits(n, m, i, j)
    {
            
        // number with all 1's
        let  allOnes = ~0;
            
        // Set all the bits in the left of j
        let left = allOnes << (j + 1);
            
        // Set all the bits in the right of j
        let right = ((1 << i) - 1);
            
        // Do Bitwise OR to get all the bits
        // set except in the range from i to j
        let mask = left | right;
            
        // clear bits j through i
        let masked_n = n & mask;
            
        // move m into the correct position
        let m_shifted = m << i;
            
        // return the Bitwise OR of masked_n
        // and shifted_m
        return (masked_n | m_shifted);
    }
     
    let n = 2, m = 4;
    let i = 2, j = 4;
 
    document.write(setBits(n, m, i, j));
     
</script>

Output : 
 



18

Reference: 
https://www.careercup.com/question?id=8863294
This article is contributed by Sahil Chhabra. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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