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Remove Trailing Zeros From a String

Difficulty: Easy

Problem Description

Given a positive integer num represented as a string, return the integer num without trailing zeros as a string.

Key Insights

  • Trailing zeros are zeros that appear at the end of a number.
  • To remove trailing zeros from a string representation of a number, we can efficiently traverse the string from the end toward the beginning until we encounter a non-zero character.
  • The constraints ensure that the input will only contain digits and will not have leading zeros.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the string. Space Complexity: O(1), as we are modifying the string without using extra space proportional to the input size.

Solution

To solve this problem, we can start from the end of the string and iterate backwards until we find the first non-zero character. We can then slice the string up to that point to remove all trailing zeros. This approach efficiently handles the removal of zeros by leveraging string indexing.

Code Solutions

def remove_trailing_zeros(num: str) -> str:
    # Start from the end of the string
    index = len(num) - 1
    # Move the index backwards until a non-zero character is found
    while index >= 0 and num[index] == '0':
        index -= 1
    # Return the substring from the start to the found index
    return num[:index + 1]
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