`assignment-s-13-1.c`¶

Problem Statement

Write a function that reverses the elements of an array in place, using only a single pointer argument, and return void.

Metadata¶

Property	Detail
Author	Amit Dutta amitdutta4255@gmail.com
Date	19 Dec 2025
License	MIT License (See the LICENSE file for details)
Difficulty	Beginner (index: 3 / 10)

Concepts¶

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Array
Pointers
Iteration
Sorting (possible)
Recursion

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Source Code¶

#include <stdio.h>
#include <stdlib.h>

void inputarr(int[], int);
void display(int[], int);
void reverse(int *);

int main()
{
    int size, *arr;
    printf("How many element do you want to add: ");
    scanf("%d", &size);
    arr = (int *)malloc((size + 1) * sizeof(int));
    inputarr(arr, size);
    printf("\n=== Before Reverse ===\n");
    display(arr, size);
    reverse(arr);
    printf("\n\n=== After Reverse ===\n");
    display(arr, size);
    free(arr);
    return 0;
}

void inputarr(int arr[], int n)
{
    int i;
    arr[0] = n;
    for (i = 1; i <= n; i++)
    {
        printf("Enter element %d: ", i);
        scanf("%d", &arr[i]);
    }
}

void display(int arr[], int n)
{
    int i;
    for (i = 1; i <= n; i++)
    {
        printf("\nIndex: %-2d | Value: %-5d | Address: %p", i, arr[i], (void *)&arr[i]);
    }
}

void reverse(int *arr)
{
    int *start = arr + 1;
    int size = *arr;
    int *end = arr + size;
    while (start < end)
    {
        *start = *start ^ *end;
        *end = *start ^ *end;
        *start = *start ^ *end;
        start++;
        end--;
    }
}

Explanation¶

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    You are explaining a C programming code to a beginner.

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    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

    - Follow the exact format below. Do NOT change headings.

    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (assignment-s-13-1.c):

    #include <stdio.h>
    #include <stdlib.h>

    void inputarr(int[], int);
    void display(int[], int);
    void reverse(int *);

    int main()
    {
        int size, *arr;
        printf("How many element do you want to add: ");
        scanf("%d", &size);
        arr = (int *)malloc((size + 1) * sizeof(int));
        inputarr(arr, size);
        printf("\n=== Before Reverse ===\n");
        display(arr, size);
        reverse(arr);
        printf("\n\n=== After Reverse ===\n");
        display(arr, size);
        free(arr);
        return 0;
    }

    void inputarr(int arr[], int n)
    {
        int i;
        arr[0] = n;
        for (i = 1; i <= n; i++)
        {
            printf("Enter element %d: ", i);
            scanf("%d", &arr[i]);
        }
    }

    void display(int arr[], int n)
    {
        int i;
        for (i = 1; i <= n; i++)
        {
            printf("\nIndex: %-2d | Value: %-5d | Address: %p", i, arr[i], (void *)&arr[i]);
        }
    }

    void reverse(int *arr)
    {
        int *start = arr + 1;
        int size = *arr;
        int *end = arr + size;
        while (start < end)
        {
            *start = *start ^ *end;
            *end = *start ^ *end;
            *start = *start ^ *end;
            start++;
            end--;
        }
    }

assignment-s-13-1.c¶