Description

Clearing the i-th bit in a number is a common bit manipulation technique. This operation involves setting the i-th bit to 0 while leaving all other bits unchanged.

Steps to Clear the i-th Bit

1. Create a Mask: Create a number that has all bits set to 1 except for the i-th bit, which is set to 0.

2. AND Operation: Perform a bitwise AND between the original number and the mask. This will clear the i-th bit while keeping all other bits unchanged.

Formula

mask =∼ (1<<𝑖)

result = num&mask

Code in Java

import java.util.*;

public class clearIthBit {
	
	public static int clearIthBit(int n, int i) {
		int bitMask = ~(1<<i);
		return n & bitMask;
	}
	public static void main(String[] args) {
		System.out.println(clearIthBit(10, 1));
	}
}

Explanation:

• Create Mask: The mask ~(1 << i) flips all bits of 1 << i. For i = 2, 1 << 2 results in 00000100, and ~00000100 results in 11111011.

• AND Operation: Performing num & mask clears the i-th bit. If num = 29 (binary 11101), then 29 & 11111011 results in 11001 (binary 11001, decimal 25).

Key Points:

Bitwise Operators:

➔ ~: Bitwise NOT (flips all bits)

➔ &: Bitwise AND

➔ <<: Left shift (shifts bits to the left)

This technique is widely used in low-level programming, graphics, networking, and other areas where efficient bit manipulation is crucial.