Remove Zeros in Decimal Representation

Difficulty: Easy | Acceptance: 76.40% | Paid: No Topics: Math, Simulation

Given an integer n, return the integer obtained by removing all trailing zeros from the decimal representation of n.

• Examples
• Constraints
• String Manipulation
• Mathematical Iteration

Examples

Example 1

Input:

n = 1020030

Output:

123

Explanation: After removing all zeros from 1020030, we get 123.

Example 2

Input:

n = 1

Output:

1

Explanation: 1 has no zero in its decimal representation. Therefore, the answer is 1.

Constraints

0 <= n <= 10^9

String Manipulation

Intuition Convert the integer to a string to easily access and remove characters from the end of the sequence.

Steps

• Convert the integer n to its string representation.
• Iterate from the end of the string and remove characters while they are ‘0’.
• If the resulting string is empty (which happens if input was 0), return 0.
• Otherwise, convert the modified string back to an integer and return it.

class Solution:
    def removeZeros(self, n: int) -> int:
        s = str(n)
        s = s.rstrip('0')
        return int(s) if s else 0

Complexity

• Time: O(log n) - The number of digits is proportional to log₁₀(n).
• Space: O(log n) - To store the string representation.
• Notes: Simple to implement but uses extra space for the string.

Mathematical Iteration

Intuition Use modulo and division operations to mathematically remove trailing zeros without converting to a string.

Steps

• While n is greater than 0 and the last digit (n % 10) is 0, divide n by 10.
• Return the resulting n.

class Solution:
    def removeZeros(self, n: int) -> int:
        while n > 0 and n % 10 == 0:
            n //= 10
        return n

Complexity

• Time: O(log n) - We iterate once per digit.
• Space: O(1) - Constant extra space used.
• Notes: Optimal space complexity and avoids string conversion overhead.