Reverse the given Array without using built in function

by SJ · June 19, 2016

Objective: Given a array, write an algorithm to reverse the array.

Example:

int a[] = {1, 2, 3, 4, 5}
Output: {5, 4, 3, 2, 1}

Approach:

It’s obvious that you cannot use any built-in function reverse it.
It’s a simple solution, we will solve it using recursive and non-recursive way.
Take 2 elements at a time, one from the from start and one from the end and swap them.
Now for recursion, Make a recursive call to rest of the string and for non-recursive solution, use the for loop and swap the elements start +1 and end +1.

Code:

Output:

Original Array[1, 2, 3, 4, 5]
Reversed - Array(Iteration):[5, 4, 3, 2, 1]
Reversed Again - Array(Recursion):[1, 2, 3, 4, 5]

Aman Rustagi

Thanks for sharing this program. Here is an alternate C program to reverse an array using recursion.
Vijay Kumar

package datastructues;

public class ReverseArray {

static int[] a = new int[] { 1, 2, 3, 4, 11, 10, 5, 6, 7, 8 };

public static void main(String[] args) {

for(int k = a.length-1; k>=0; k–)
{
System.out.println(a[k]);
}

recurse(a, a.length -1);

int[] reverseArray = reverseArray(a);

System.out.println(reverseArray);
}
private static void recurse(int[] a, int total) {
if(total >= 0)
{
System.out.println(a[total]);
recurse(a, –total);
}
}

private static int[] reverseArray(int[] a)
{
for (int i = 1; i <= a.length / 2; i++) {
a[i-1] = a[i-1] + a[a.length-i];
a[a.length-i] = a[i-1] – a[a.length-i];
a[i-1] = a[i-1] – a[a.length-i];
}
return a;
}
}