Search Insert Position

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You may assume no duplicates in the array.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

Solution:
Binary Search + boundaries check. 

public class Solution {
    public int searchInsert(int[] A, int target) {
        return binarySearch(A, 0, A.length-1, target);
    }
    public int binarySearch(int[] A, int first, int last, int target){
        int mid = (first+last)/2;
        if (last < first) return -1;
        
        if(A[first] > target){
            return first;
        }
        if(A[last] < target){
            return last+1;   
        } 
        
        if(A[mid] == target){ 
            return mid;
        }
        else if(A[mid] > target){
            return binarySearch(A, first, mid-1, target);
        }
        else{
            return binarySearch(A, mid+1, last, target);
        }
        
    }
}