How do you approach Power of Two?

A power of two in binary has exactly one '1' bit.

What is the time complexity of Power of Two?

Time complexity: O(1). Space complexity: O(1).

What are common mistakes on Power of Two?

Overflowing at an intermediate step even though the final answer fits. Assuming a modulo is non-negative. In most languages -1 % n is negative, which breaks cyclic indexing. Testing floating-point values for exact equality where integer arithmetic would have been exact.

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Power of Two

EasyAlgorithms

Description

Given an integer `n`, return `true` if it is a power of two. Otherwise, return `false`. An integer `n` is a power of two if there exists an integer `x` such that `n == 2^x`.

Example 1

Input: n = 1

Output: true

Explanation: 2^0 = 1

Example 2

Input: n = 16

Output: true

Explanation: 2^4 = 16

Example 3

Input: n = 3

Output: false

Constraints

- -2^31 <= n <= 2^31 - 1

Power of Two: approach, complexity and pitfalls

An easy math problem, graded against 8 test cases (5 of them hidden).

The pattern: Math

Number theory, digit manipulation, and closed-form reasoning.

Reach for it when you see: Primes, digits, base conversion, or a problem with a formula hiding behind it.

More Mathproblems →

If you are stuck

Show the 3-step hint ladder

A power of two in binary has exactly one '1' bit.
Think about what n & (n - 1) does for a power of two.
Make sure to handle edge cases like n <= 0.

The optimal approach

Show the approach: Bit Manipulation

A power of two in binary representation has exactly one bit set to 1 (e.g., 1 = 1, 2 = 10, 4 = 100, 8 = 1000).

The trick: `n & (n - 1)` removes the lowest set bit. For a power of two, this results in 0. Combined with the check that `n > 0`, this gives us an O(1) solution.

Time: O(1)
Space: O(1)

The full reference solution in every supported language stays in the editor above - reveal it there once you have had a real attempt.

What the tests check

Read off this problem's own test suite, so these are the cases a submission actually has to survive.

Negative numbers. The suite includes negative values. Running-sum, min/max seeding and any "initialise to zero" step need to handle them.
Zero. Zero appears in the input, which is the value most likely to break a truthiness check used in place of an explicit comparison.

Common Math mistakes

These apply to the pattern as a whole, not just this problem.

Overflowing at an intermediate step even though the final answer fits.
Assuming a modulo is non-negative. In most languages `-1 % n` is negative, which breaks cyclic indexing.
Testing floating-point values for exact equality where integer arithmetic would have been exact.

← Back to problems

Power of Two

EasyAlgorithms

Description

Given an integer `n`, return `true` if it is a power of two. Otherwise, return `false`. An integer `n` is a power of two if there exists an integer `x` such that `n == 2^x`.

Example 1

Input: n = 1

Output: true

Explanation: 2^0 = 1

Example 2

Input: n = 16

Output: true

Explanation: 2^4 = 16

Example 3

Input: n = 3

Output: false

Constraints

- -2^31 <= n <= 2^31 - 1

Power of Two: approach, complexity and pitfalls

An easy math problem, graded against 8 test cases (5 of them hidden).

The pattern: Math

Number theory, digit manipulation, and closed-form reasoning.

Reach for it when you see: Primes, digits, base conversion, or a problem with a formula hiding behind it.

More Mathproblems →

If you are stuck

Show the 3-step hint ladder

A power of two in binary has exactly one '1' bit.
Think about what n & (n - 1) does for a power of two.
Make sure to handle edge cases like n <= 0.

The optimal approach

Show the approach: Bit Manipulation

A power of two in binary representation has exactly one bit set to 1 (e.g., 1 = 1, 2 = 10, 4 = 100, 8 = 1000).

The trick: `n & (n - 1)` removes the lowest set bit. For a power of two, this results in 0. Combined with the check that `n > 0`, this gives us an O(1) solution.

Time: O(1)
Space: O(1)

The full reference solution in every supported language stays in the editor above - reveal it there once you have had a real attempt.

What the tests check

Read off this problem's own test suite, so these are the cases a submission actually has to survive.

Negative numbers. The suite includes negative values. Running-sum, min/max seeding and any "initialise to zero" step need to handle them.
Zero. Zero appears in the input, which is the value most likely to break a truthiness check used in place of an explicit comparison.

Common Math mistakes

These apply to the pattern as a whole, not just this problem.

Overflowing at an intermediate step even though the final answer fits.
Assuming a modulo is non-negative. In most languages `-1 % n` is negative, which breaks cyclic indexing.
Testing floating-point values for exact equality where integer arithmetic would have been exact.