How to Remove Duplicates in an Array in C

How to Remove Duplicates in an Array in C ?

Answer

To remove duplicates from an array in C, you can use loops with a temporary array or a flag array to filter out duplicate elements.

✐ Examples

1 Remove Duplicates using Temporary Array

In this example,

We create an array named `numbers` with duplicate integers.
We use a loop to check for duplicates and store unique elements in a temporary array.
Finally, we get an array without duplicates using the temporary array.

C Program

#include <stdio.h>

int main() {
    int numbers[] = {1, 2, 2, 3, 4, 4, 5};
    int n = sizeof(numbers) / sizeof(numbers[0]);
    int temp[n];
    int j = 0;
    for (int i = 0; i < n; i++) {
        int duplicate = 0;
        for (int k = 0; k < j; k++) {
            if (numbers[i] == temp[k]) {
                duplicate = 1;
                break;
            }
        }
        if (!duplicate) {
            temp[j++] = numbers[i];
        }
    }
    printf("Array without duplicates: ");
    for (int i = 0; i < j; i++) {
        printf("%d ", temp[i]);
    }
    return 0;
}

Output

Array without duplicates: 1 2 3 4 5

2 Remove Duplicates using Flag Array

In this example,

We create an array named `numbers` with duplicate integers.
We use a flag array to mark duplicate elements and filter out unique elements.
Finally, we get an array without duplicates using the flag array.

C Program

#include <stdio.h>

int main() {
    int numbers[] = {1, 2, 2, 3, 4, 4, 5};
    int n = sizeof(numbers) / sizeof(numbers[0]);
    int visited[n];
    for (int i = 0; i < n; i++) {
        visited[i] = 0;
    }
    printf("Array without duplicates: ");
    for (int i = 0; i < n; i++) {
        if (!visited[i]) {
            printf("%d ", numbers[i]);
            for (int j = i + 1; j < n; j++) {
                if (numbers[i] == numbers[j]) {
                    visited[j] = 1;
                }
            }
        }
    }
    return 0;
}

Output

Array without duplicates: 1 2 3 4 5

Summary

In this tutorial, we learned How to Remove Duplicates in an Array in C language with well detailed examples.

◀ Previous Next ▶

C Tutorials

C How-Tos

How to Remove Duplicates in an Array in C

How to Remove Duplicates in an Array in C ?

Answer

✐ Examples

1 Remove Duplicates using Temporary Array

C Program

Output

2 Remove Duplicates using Flag Array

C Program

Output

Summary

More C Arrays Tutorials