C PROGRAMMING PROGRAM • ARRAYS, SEARCHING & SORTING

Reverse an Array

Learn how to reverse an array using a clear C program.

BeginnerArraysTwo pointersIn-place swap

PROBLEM UNDERSTANDING

Input and expected output

Sample input

5
1 2 3 4 5

Sample output

Reversed: 5 4 3 2 1

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 left = 0, right = size - 1; left < right; left++, right--) {
        int temporary = values[left];
        values[left] = values[right];
        values[right] = temporary;
    }
    printf("Reversed: ");
    for (int index = 0; index < size; index++) printf("%d%c", values[index], index == size - 1 ? '\n' : ' ');
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Reversed: 5 4 3 2 1

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Swap elements at symmetric left and right indices until the pointers meet.
Display the computed result.

Swap elements at symmetric left and right indices until the pointers meet.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

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.