Program to Reverse an Array Elements In Place.

Input: arr[] = {9, 2, 7, 3, 10}
Output: arr[] = {10, 3, 7, 2, 9}

• Declare two variables, start = 0 and end = n-1 where n is the size of the given array.
• Run a while loop and keep swapping arr[start] and arr[end] and after each swap increment the value of start = start + 1 and decrement the value of end  = end - 1. 
• Break the loop condition as soon as start >= end.

//C++ code to reverse the array elements
#include<bits/stdc++.h>
using namespace std;

//function to reverse array
void reverseArray(int arr[], int n){

    int start = 0, end = n - 1;

    while(start < end){
        int temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
}

int main(){
    
    int arr[] = {9, 2, 7, 3, 10};
    //size of given array
    int n = sizeof(arr)/sizeof(arr[0]);
    reverseArray(arr, n);

    for(int i = 0; i < n; i++){
        cout<<arr[i]<<" ";
    }

    return 0;
}

10, 3, 7, 2, 9

• Time Complexity: O(n)
• Space Complexity: (1)