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

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 modifed in 4th step).
  7. The result will be N with M as substring from ith to jth bits

C++


[sourcecode language=”CPP” highlight=”5-30″]
// 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;
}
[/sourcecode]

Java


[sourcecode language=”Java” highlight=”4-30″]
// 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
[/sourcecode]

Python


[sourcecode language=”Python” highlight=””]
# 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
[/sourcecode]

C#


[sourcecode language=”csharp” highlight=”6-32″]
// 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.
[/sourcecode]


Output:

18

Reference:
https://www.careercup.com/question?id=8863294

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