## The challenge#

Given a sorted (in ascending order) integer array `nums` of `n` elements and a `target` value, write a function to search `target` in `nums`. If `target` exists, then return its index, otherwise return `-1`.

Example 1:

```Input: `nums` = [-1,0,3,5,9,12], `target` = 9
Output: 4
Explanation: 9 exists in `nums` and its index is 4```

Example 2:

```Input: `nums` = [-1,0,3,5,9,12], `target` = 2
Output: -1
Explanation: 2 does not exist in `nums` so return -1```

Note:

1. You may assume that all elements in `nums` are unique.
2. `n` will be in the range `[1, 10000]`.
3. The value of each element in `nums` will be in the range `[-9999, 9999]`.

## The solution in Java code#

We call the `search()` method which recursively calls the `binarySearch()` method for each level.

If we find the target, then we pass back the layer as an integer.

``````class Solution {
private int[] nums;
private int target;

public int search(int[] nums, int target) {
this.nums = nums;
this.target = target;

return binarySearch(0, this.nums.length-1);
}

private int binarySearch(int start, int end) {
if (start>end) return -1;

int m = start+end;

if (this.target==this.nums[m]) return m;
else if (this.target<nums[m]) return binarySearch(start, m-1);
else return binarySearch(m+1, end);
}

}
``````