karl.wy_个人页

public class Solution {
    public int binarySearch(int[] nums, int target) {
        if (nums == null || nums.length == 0) {
            return -1;
        }
        return helper(nums, target, 0, nums.length-1);
    }
    private int helper(int[] nums, int target, int start, int end) {
        if (start>end) {
            return -1;
        }
        int mid = start + (end-start)/2;
        if (nums[mid] == target) {
            return mid;
        } if (nums[mid] < target) {
            return helper(nums, target, mid+1, end);
        } else {
            return helper(nums, target, start, mid-1);
        }
    }
}