Array Deletion at End in DSA C

Mental Model

Removing the last item from a list means just ignoring it from now on.

Analogy: Think of a stack of plates where you only take the top plate off to remove it.

Index: 0   1   2   3   4
Array: 10 -> 20 -> 30 -> 40 -> 50
Size: 5

Dry Run Walkthrough

Input: array: [10, 20, 30, 40, 50], delete last element

Goal: Remove the last element and reduce the size by one

Step 1: Check if array is empty

10 -> 20 -> 30 -> 40 -> 50, size=5

Why: We must ensure there is something to delete

Step 2: Reduce size by 1 to remove last element

10 -> 20 -> 30 -> 40, size=4

Why: Reducing size ignores the last element effectively deleting it

Step 3: Print updated array

10 -> 20 -> 30 -> 40, size=4

Why: To confirm the last element is removed

Result:

10 -> 20 -> 30 -> 40 -> null

Annotated Code

DSA C

#include <stdio.h>

void deleteAtEnd(int arr[], int *size) {
    if (*size == 0) {
        printf("Array is empty, nothing to delete.\n");
        return;
    }
    (*size)--; // reduce size by 1 to delete last element
}

void printArray(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        printf("%d", arr[i]);
        if (i != size - 1) printf(" -> ");
    }
    printf(" -> null\n");
}

int main() {
    int arr[5] = {10, 20, 30, 40, 50};
    int size = 5;

    deleteAtEnd(arr, &size);
    printArray(arr, size);

    return 0;
}

if (*size == 0) {

Check if array is empty to avoid deleting from empty array

(*size)--;

Reduce size by one to remove last element logically

for (int i = 0; i < size; i++) {

Traverse array up to current size to print elements

Output

10 -> 20 -> 30 -> 40 -> null

Complexity Analysis

Time: O(1) because deleting last element just reduces size without shifting

Space: O(1) because no extra space is needed for deletion

vs Alternative: Compared to deleting from start or middle which requires shifting O(n), this is faster and simpler

Edge Cases

empty array

Prints message and does not change array

DSA C

if (*size == 0) {

array with one element

Size reduces to zero, array becomes empty

DSA C

(*size)--;

When to Use This Pattern

When you need to remove the last item quickly without rearranging others, use array deletion at end because it only changes size.

Common Mistakes

Mistake: Trying to shift elements after deleting last element
Fix: No shifting needed; just reduce size by one

Mistake: Not checking if array is empty before deletion
Fix: Add a check for size zero before deleting

Summary

Deletes the last element by reducing the array size by one.

Use when you want to remove the last item quickly without moving other elements.

The key is that reducing size ignores the last element without shifting.