Reverse a string using a stack

Easy

≈ 8 minute session

Summary

Reverse the characters of a string by simulating a stack.

Problem statement

Given an input string s, return a new string that is the reverse of s. Implement the reversal by using a stack (i.e., push all characters onto a stack and then pop them to build the reversed string). Avoid using Python slicing like s[::-1] to ensure the stack logic is used.

Task

Use a stack (LIFO) approach to reverse and return the input string.

Examples

Reverse 'hello'

Input

reverse_with_stack('hello')

Output

'olleh'

Explanation

Characters pushed then popped produce the reversed string.

Input format

A single string s. Example: 'hello'

Output format

Return the reversed string.

Constraints

0 <= len(s) <= 10^5. Aim for O(n) time and O(n) extra space for the stack.

Samples

Sample input 0

reverse_with_stack('abc')

Sample output 0

'cba'

Explanation 0

Reverses characters 'a','b','c' to 'cba'.

Code editor

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03:42 PM

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