LeetCode 1556. Thousand Separator

Description

https://leetcode.com/problems/thousand-separator/

Given an integer n, add a dot (“.”) as the thousands separator and return it in string format.

Example 1:

Input: n = 987
Output: "987"

Example 2:

Input: n = 1234
Output: "1.234"

Example 3:

Input: n = 123456789
Output: "123.456.789"

Example 4:

Input: n = 0
Output: "0"

Constraints:

  • 0 <= n < 2^31

Explanation

Convert the integer to string and add “.” on every 3 characters.

Python Solution

class Solution:
    def thousandSeparator(self, n: int) -> str:
        result = []
        
        n_str = str(n)
        for i, c in enumerate(n_str[::-1]):
            if i != 0 and i % 3 == 0:
                result.insert(0, ".")    
                
            result.insert(0, c)
            

        return "".join(result)
            
            
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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