Leetcode: Shuffle String

Problem:

https://leetcode.com/problems/shuffle-string/

Code:

class Solution:
    def restoreString(self, s: str, indices: List[int]) -> str:
        result=['']*len(s)
        for i, index in enumerate(indices):
            result[index] = s[i]
        return ''.join(result)

Key Points:

• You are given: s → original string indices → target positions for each character of s

• The rule: s[i] must be placed at position indices[i] in the final string.

• Create a result array of the same length: result = [''] * len(s) (Using a list because strings are immutable in Python.)

• Loop through each character: for i, index in enumerate(indices): result[index] = s[i] → This directly places every character into its correct final position.

• Finally, join the list into a string: ''.join(result)

• Why this works:

  • Direct index placement avoids extra scans.

  • No need for sorting or complex operations.

  • Perfect for one-pass O(n) reconstruction.

• Time Complexity: O(n)

• Space Complexity: O(n) for the result list