Invert k-th Most Significant Bits of N in Java

9 May 2025 | 3 min read

Problem Statement

Inverting the k-th most significant bit (MSB) of a number N involves flipping the bit at position k, counting from the leftmost bit.

Solution to The Problem

The process is as follows:

Create a mask: A mask with 1 at the k-th position.
Use XOR: Apply XOR to invert the bit. If the bit is 1, it becomes 0; if the bit is 0, it becomes 1.

For example, for N = 59 (binary 111011) and k = 3, inverting the 3rd bit results in 51 (binary representation 110011). This technique is useful in bitwise operations for tasks like flag manipulation.

Example 1:

Input: N = 10, K = 1

Output: 2

The binary form of 10 is 1010. When the first bit is inverted, it turns into 0010, which has a decimal value of 2.

Example 2:

Input: N = 32, K = 2

Output: 48

The binary form of 32 is 100000. By flipping the second bit, it changes to 110000, which has a decimal value of 48.

Bit Manipulation Approach

First, determine the total number of bits in N. If the number of bits is less than K, return N as the result. Otherwise, flip the K-th most significant bit of N and then return the new number obtained after the flip.