Index of last occurrence GFG

 package com.company;

public class LastIndex {
//    Index of last occurrence
//    1. Naive solution
    public static int index(int[] arr, int x) {
        int n = arr.length;
        for(int i = n - 1; i >= 0; i--) {
            if(arr[i] == x) {
                return i;
            }
        }
        return -1;
    }

//    2. Efficient iterative solution
    public static int lastIndex(int[] arr, int x) {
        int n = arr.length;
        int low = 0; int high = n - 1;
        while(low <= high) {
            int mid = (low + high) / 2;
            if(arr[mid] == x) {
                if(mid == n - 1 || arr[mid + 1 ] != x) {
                    return mid;
                }
                else
                    low = mid + 1;
            }

            else if(arr[mid] > x) {
                high =mid - 1;
            }
            else
                low = mid + 1;
        }
        return -1;
    }

//    3. Recursive approach
    public static int indexOfLastOccurrence(int[] arr, int x, int low, int high) {
        int n = arr.length;
        if(low > high){
            return -1;
        }
        int mid = (low + high) / 2;

        if(arr[mid] == x){
            if(mid == n - 1 || arr[mid + 1] != arr[mid]) {
                return mid;
            }
            else
                return indexOfLastOccurrence(arr, x, mid + 1, high);
        }

        else if(arr[mid] > x) {
            return indexOfLastOccurrence(arr, x, low, mid - 1);
        }

        else
            return indexOfLastOccurrence(arr, x, mid + 1, high);

    }
    public static void main(String[] args) {
        int[] array = {1,2,2,2,2,4,4,5,5,6};
        System.out.println(indexOfLastOccurrence(array, 22, 0, 9));
    }
}