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This is a Medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Box.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Box during technical interviews.

Flip a specific bit in an integer

Company: Box

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: Medium

Interview Round: Onsite

Given a non-negative integer num and a zero-based bit position p, return the integer resulting from flipping only the bit at position p (i.e., 0 becomes 1, 1 becomes 0). Explain your approach and its time/space complexity.

Quick Answer: This question evaluates a candidate's understanding of bitwise operations and low-level integer manipulation, along with the ability to reason about the time and space complexity of bit-level operations.

Given a non-negative integer `num` and a zero-based bit position `p`, return the integer that results from flipping ONLY the bit at position `p` (a `0` becomes `1`, a `1` becomes `0`). All other bits remain unchanged. The bit at position `p` has place value 2^p. Flipping it is a classic application of the XOR operator: XOR-ing any bit with `1` toggles it, while XOR-ing with `0` leaves it unchanged. So building a mask with a single `1` at position `p` (`1 << p`) and XOR-ing it with `num` flips exactly that one bit. Example: `num = 5` (binary `101`), `p = 1`. The mask `1 << 1` is `010`. `101 ^ 010 = 111 = 7`. Return the resulting integer.

Constraints

0 <= num (non-negative integer)
0 <= p (zero-based bit position)
Flipping a bit at a position beyond num's highest set bit simply sets that bit to 1.
Python integers are arbitrary-precision, so very large p values are handled natively.

Examples

Input: (5, 0)

Expected Output: 4

Explanation: 5 is 101. Bit 0 is 1, so it clears to 0: 100 = 4.

Input: (5, 1)

Expected Output: 7

Explanation: 5 is 101. Bit 1 is 0, so it sets to 1: 111 = 7.

Input: (0, 0)

Expected Output: 1

Explanation: 0 is 0. Flipping bit 0 sets it: 1.

Input: (8, 3)

Expected Output: 0

Explanation: 8 is 1000. Bit 3 is the only set bit; flipping it clears the number to 0.

Input: (0, 31)

Expected Output: 2147483648

Explanation: Flipping bit 31 of 0 yields 2^31 = 2147483648, showing high-bit positions work.

Input: (1023, 5)

Expected Output: 991

Explanation: 1023 is 1111111111. Clearing bit 5 (value 32) gives 1023 - 32 = 991.

Input: (7, 10)

Expected Output: 1031

Explanation: 7 is 111. Bit 10 is beyond the top set bit, so flipping it just adds 2^10 = 1024: 7 + 1024 = 1031.

Hints

Which bitwise operator toggles a bit: AND, OR, or XOR? Recall that x ^ 1 = NOT x and x ^ 0 = x.
Build a mask with a single 1 at position p using a left shift: 1 << p.
XOR the number with that mask: num ^ (1 << p). This flips only the targeted bit and leaves every other bit untouched, in O(1) time and space.

Quick Overview

This question evaluates a candidate's understanding of bitwise operations and low-level integer manipulation, along with the ability to reason about the time and space complexity of bit-level operations.