#2710

Easy

auto_awesomeString-driven solution strategy

LeetCode Problem Workspace

Remove Trailing Zeros From a String

Remove trailing zeros from a string representing a positive integer number.

Problem Statement

You are given a positive integer num represented as a string. Your task is to return the integer num as a string, with all trailing zeros removed.

The input string only contains digits, and the length of num can be up to 1000 characters. There are no leading zeros in the input string.

Examples

Example 1

Input: num = "51230100"

Output: "512301"

Integer "51230100" has 2 trailing zeros, we remove them and return integer "512301".

Example 2

Input: num = "123"

Output: "123"

Integer "123" has no trailing zeros, we return integer "123".

Constraints

1 <= num.length <= 1000
num consists of only digits.
num doesn't have any leading zeros.

Solution Approach

Simple String Trim

Iterate through the string from right to left, removing zeros until a non-zero digit is encountered. Return the modified string.

Using String Methods

Use Python's rstrip() method to remove trailing zeros from the string, as it's an efficient and straightforward solution.

Manual String Manipulation

Manually traverse the string from the end, counting the zeros and trimming them without using built-in functions.

Complexity Analysis

Metric	Value
Time	Depends on the final approach
Space	Depends on the final approach

The time complexity for this problem is O(n), where n is the length of the string. Space complexity depends on the method chosen, ranging from O(1) with in-place manipulation to O(n) with string operations.

What Interviewers Usually Probe

Look for the candidate’s understanding of string manipulation and edge case handling.
Evaluate how they handle the potential inefficiency of large string sizes.
Test if they can provide a clear solution for non-zero trimming using string methods.

Common Pitfalls or Variants

Common pitfalls

Failing to handle edge cases where there are no trailing zeros.
Misunderstanding the requirement for string manipulation versus integer-based solutions.
Not considering the potential impact on performance with large strings.

Follow-up variants

Consider variations where the input string contains only zeros.
Explore edge cases where the number is a single-digit integer with no trailing zeros.
Evaluate solutions that also account for leading zeros (if applicable in different scenarios).

FAQ

What is the main approach to solving "Remove Trailing Zeros From a String"?

The main approach involves string manipulation, specifically removing trailing zeros by iterating from the end of the string or using built-in methods like rstrip().

How do you handle strings with no trailing zeros?

If no trailing zeros are present, simply return the original string as no changes are necessary.

Can I use integer-based solutions for this problem?

No, the problem specifically requires working with a string representation, so integer-based solutions won't work for removing trailing zeros.

What if the input string contains only zeros?

In that case, the output should be "0", as a string of zeros should be reduced to a single zero.

What is the time complexity of the solution?

The time complexity is O(n), where n is the length of the string, as we must check each character from the end to the start.

terminal

Solution

Solution 1: Traversal

We can traverse the string from the end to the beginning, stopping when we encounter the first character that is not `0`. Then, we return the substring from the beginning to this character.

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class Solution:
    def removeTrailingZeros(self, num: str) -> str:
        return num.rstrip("0")

Continue Practicing

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