Go Slice – Remove Duplicates

Go – Slice Remove Duplicates

In Go, slices are dynamic collections that can contain duplicate elements. Removing duplicates involves creating a new slice that includes only unique elements from the original slice. Go does not provide a built-in function for this, so you need to implement custom logic using maps or loops.

In this tutorial, we will explore how to remove duplicate elements from a slice with practical examples and detailed explanations.

Steps to Remove Duplicates from a Slice

Initialize a Map: Use a map to track elements that have already been added to the new slice.
Iterate Through the Slice: Use a loop to check if an element exists in the map.
Append Unique Elements: Add elements that are not in the map to the new slice and update the map.

Examples of Removing Duplicates from a Slice

1. Remove Duplicates from a Slice of Integers

This example demonstrates how to remove duplicates from a slice of integers using a map:

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package main

import "fmt"

// Function to remove duplicates from a slice of integers
func removeDuplicates(slice []int) []int {
    uniqueMap := make(map[int]bool)
    result := []int{}
    for _, v := range slice {
        if !uniqueMap[v] {
            uniqueMap[v] = true
            result = append(result, v)
        }
    }
    return result
}

func main() {
    // Declare and initialize a slice with duplicates
    numbers := []int{10, 20, 20, 30, 40, 40, 50}

    // Remove duplicates
    uniqueNumbers := removeDuplicates(numbers)

    // Print the result
    fmt.Println("Original Slice:", numbers)
    fmt.Println("Slice without Duplicates:", uniqueNumbers)
}

Explanation

Initialize Map: A map uniqueMap is used to track elements that have already been added to the result slice.
Iterate Through Slice: The loop checks if an element exists in the map. If it doesn’t, the element is added to both the map and the result slice.
Return Result: The new slice containing only unique elements is returned.
Print Results: The original and updated slices are printed in the main function.

Output

2. Remove Duplicates from a Slice of Strings

This example demonstrates how to remove duplicates from a slice of strings:

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package main

import "fmt"

// Function to remove duplicates from a slice of strings
func removeDuplicates(slice []string) []string {
    uniqueMap := make(map[string]bool)
    result := []string{}
    for _, v := range slice {
        if !uniqueMap[v] {
            uniqueMap[v] = true
            result = append(result, v)
        }
    }
    return result
}

func main() {
    // Declare and initialize a slice with duplicates
    words := []string{"apple", "banana", "apple", "cherry", "banana", "date"}

    // Remove duplicates
    uniqueWords := removeDuplicates(words)

    // Print the result
    fmt.Println("Original Slice:", words)
    fmt.Println("Slice without Duplicates:", uniqueWords)
}

Explanation

Initialize Map: A map uniqueMap is used to track strings that have already been added to the result slice.
Iterate Through Slice: The loop checks if a string exists in the map. If it doesn’t, the string is added to both the map and the result slice.
Return Result: The new slice containing only unique strings is returned.
Print Results: The original and updated slices are printed in the main function.

Output

Points to Remember

Use Maps: Maps are efficient for tracking unique elements in a slice, as they provide O(1) lookup time.
Generic Logic: The same logic can be applied to slices of any type, such as integers, strings, or structs, by modifying the map key type.
Preserve Order: The examples above preserve the original order of elements in the slice.
Memory Usage: Removing duplicates requires additional memory for the map and the result slice.

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How to Remove Duplicates in Slice in Go