C PROGRAMMING PROGRAM • ARRAYS, SEARCHING & SORTING

Remove Duplicate Elements from an Array

Learn how to remove duplicate elements from an array using a clear C program.

IntermediateArraysDuplicate removalNested loops

PROBLEM UNDERSTANDING

Input and expected output

Sample input

8
3 5 3 2 5 7 2 9

Sample output

Unique array: 3 5 2 7 9

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int size, values[100];

    printf("Enter array size: ");
    scanf("%d", &size);
    if (size < 1 || size > 100) return 1;
    for (int index = 0; index < size; index++) scanf("%d", &values[index]);
    for (int index = 0; index < size; index++) {
        for (int next = index + 1; next < size;) {
            if (values[next] == values[index]) {
                for (int shift = next; shift < size - 1; shift++) values[shift] = values[shift + 1];
                size--;
            } else {
                next++;
            }
        }
    }
    printf("Unique array: ");
    for (int index = 0; index < size; index++) printf("%d%c", values[index], index == size - 1 ? '\n' : ' ');
    return 0;
}

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EXPECTED OUTPUT FOR THE SAMPLE

Unique array: 3 5 2 7 9

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
When a duplicate is found, shift later elements left and reduce the logical size.
Display the computed result.

When a duplicate is found, shift later elements left and reduce the logical size.

EFFICIENCY

Time and space complexity

Time complexity

O(n²)

Auxiliary space

O(n)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.