binarySearch 递归写法

//Given an array of integers nums which is sorted in ascending order,
// and an integer target, write a function to search target in nums.
// If target exists, then return its index. Otherwise, return -1.
//
//You must write an algorithm with O(log n) runtime complexity

public class Solution {
    public int search(int[] nums, int target) {
        return binarySearch(nums, 0, nums.length, target);
    }

    public int binarySearch(int[] nums, int l, int r, int target) {
        if (l == r) {
            return -1;
        }
        if (r - l == 1) {
            if (nums[l] != target) {
                return -1;
            }
            return l;
        }

        int mid = (l + r) / 2;
        if (nums[mid] > target) {
            return binarySearch(nums, l, mid, target);
        }
        return binarySearch(nums, mid, r, target);
    }
}