GO Lang Interview Question: Reverse A String in n/2 Complexity!

GO Lang Interview Question: Reverse A String in n/2 Complexity!

In Go language (Golang), understanding how to efficiently reverse a string is crucial for optimizing performance in various applications. Let's explore a common interview question where we aim to reverse a string with a time complexity of O(n/2).

Understanding the Problem

When asked to reverse a string in Golang with a complexity of O(n/2), the goal is to achieve this task with a time complexity linearly proportional to half the length of the string. This ensures efficient execution, especially for longer strings, without compromising on readability and simplicity.

Approach and Solution

Approach 1: Using Runes

In Go, strings are immutable, so we convert the string to a mutable format using runes, which represent Unicode code points. Here’s how we can achieve the reversal:

package main

import (

func reverseString(s string) string {
    runes := []rune(s)
    length := len(runes)

    for i := 0; i < length/2; i++ {
        // Swap characters from the start and end
        runes[i], runes[length-1-i] = runes[length-1-i], runes[i]

    return string(runes)

func main() {
    str := "Hello, Golang!"
    fmt.Println("Original:", str)
    reversed := reverseString(str)
    fmt.Println("Reversed:", reversed)


  • FunctionreverseString: This function takes a string s and converts it into a slice of runes ([]rune(s)).

  • Reversing Process: It iterates only up to half of the string's length (length/2) and swaps characters from the start (runes[i]) with characters from the end (runes[length-1-i]).

  • Returning the Reversed String: Finally, the function converts the slice of runes back into a string and returns the reversed string.

Complexity Analysis

The time complexity of this approach is O(n/2), where n is the length of the string. This means the function performs operations proportional to half the string's length, ensuring efficient execution even for longer strings.


In Golang interviews, mastering the manipulation of strings efficiently is essential. By understanding and implementing the O(n/2) complexity approach to reversing strings using runes, developers can showcase their ability to write optimized and concise code. This approach not only demonstrates proficiency in Go language fundamentals but also highlights problem-solving skills in handling string operations effectively. Practice and familiarity with such techniques are valuable for excelling in technical interviews and real-world applications alike.

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