Check Cube Number in Python

What You’ll Learn

A perfect cube is an integer n = k3 for some integer k. This tutorial covers float estimate + verify, pure integer search, binary search, a live preview, worked Python examples, edge cases, and complexity.

📝 Problem & Approach

Given an integer n, decide whether n = k³ for some integer k.

# 27 = 3**3  → yes
# 28 sits between 3**3 and 4**3 → no
# -8 = (-2)**3 → yes

Inputs & Outputs

Minimal workflow

function is_perfect_cube(n):
    x = abs(n)
    k = 0
    while k * k * k < x:
        k = k + 1
    return k * k * k == x

Method comparison

🔮 Live Preview

JavaScript safe integers. Uses integer scan on absolute value, then applies sign logic.

Press “Check cube” to classify the number.

Examples Gallery

Three complete Python programs — float estimate + verify, integer range scan, and binary search. Click View Output to reveal sample console results.

def is_cube(number: int) -> bool:
    k = round(abs(number) ** (1 / 3))
    if number < 0:
        k = -k
    return k * k * k == number


input_number = 27
if is_cube(input_number):
    print(f"{input_number} is a cube number.")
else:
    print(f"{input_number} is not a cube number.")

27 is a cube number.

def is_cube_number(num: int) -> bool:
    k = 0
    while k * k * k < num:
        k += 1
    return k * k * k == num


print("Cube numbers in the range 1 to 50:")
for i in range(1, 51):
    if is_cube_number(i):
        print(i, end=" ")

Cube numbers in the range 1 to 50:
1 8 27

def is_cube_binary(n: int) -> bool:
    x = abs(n)
    lo, hi = 0, x
    while lo <= hi:
        mid = (lo + hi) // 2
        cube = mid * mid * mid
        if cube == x:
            return True
        if cube < x:
            lo = mid + 1
        else:
            hi = mid - 1
    return False


for value in (27, 28, -8, 0, 64):
    print(f"{value}: {'cube' if is_cube_binary(value) else 'not a cube'}")

27: cube
28: not a cube
-8: cube
0: cube
64: cube

🔎 Worked Walkthrough — n = 28

Trace the integer scan. Cubes nearby: 27 = 3³, 64 = 4³.

Final: 28 is not a perfect cube.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

For scan-based methods, n denotes input magnitude and root growth is about |n|^(1/3).

💡 Best Practices