Tag: reverse array

Lets write a c program to copy elements of one array to another array in reverse order. Hint: Make use of macros to assign size of the array. And both the arrays must have same size.

Related Read:
Basics of Arrays: C Program

Example: Expected Output

Enter 5 integer numbers
5
2
6
4
3

Copying elements from array a to b
In reverse Order

Original(a[5]) –> Copy(b[5])
5 –> 3
2 –> 4
6 –> 6
4 –> 2
3 –> 5

Video Tutorial: C Program To Copy Elements of One Array To Another In Reverse Order

Source Code: C Program To Copy Elements of One Array To Another In Reverse Order

#include<stdio.h>

#define N 5

int main()
{
    int a[N], b[N], i, j;

    printf("Enter %d integer numbers\n", N);
    for(i = 0; i < N; i++)
        scanf("%d", &a[i]);

    printf("\n\nCopying elements from array a to b, in reverse order\n");
    for(i = N - 1, j = 0; i >= 0; i--, j++)
        b[j] = a[i];

    printf("\nOriginal(a[%d])  -->  Copy(b[%d])\n", N, N);
    for(i = 0; i < N; i++)
        printf("%4d\t\t-->%6d\n", a[i], b[i]);

    return 0;
}

Output:
Enter 5 integer numbers
1
2
3
4
5

Copying elements from array a to b, in reverse order

Original(a[5]) –> Copy(b[5])
1 –> 5
2 –> 4
3 –> 3
4 –> 2
5 –> 1

Logic To Copy Elements of One Array To Another In Reverse Order

We ask the user to enter N integer numbers. N is macro which is used to define size of the array. We store the user entered numbers inside array variable a. We initialize the variable i to last index of array a, and we initialize the variable j to first index of array variable b. Now for each iteration of the for loop, we assign the value of a[i] to b[j]. For each iteration of for loop we decrement the value of i by 1 and increment the value of j by 1. For loop iterates until i value is greater than or equal to 0.

At the end we print / display the content of both original array(a[5]) and the array to which the elements are copied to(b[5]) in reverse order.

Explanation With Example

If int a[5] = {5, 2, 6, 4, 3};

    for(i = N - 1, j = 0; i >= 0; i--, j++)
        b[j] = a[i];

a[5] = {5, 2, 6, 4, 3};
b[5] = {3, 4, 6, 2, 5};

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