LeetCode--704. Binary Search

二分查找的两种写法：

1、循环：

class Solution {
    public int search(int[] nums, int target) {
        if(nums == null) {
            return -1;
        }
        int lo = 0;
        int hi = nums.length - 1;
        while(lo <= hi) {
            int mid = (lo + hi) / 2;
            if(target > nums[mid]) {
                lo = mid + 1;
            } else if(target < nums[mid]) {
                hi = mid - 1;
            } else {
                return mid;
            }
        }
        return -1;
    }
}

2、递归：

class Solution {
    public int search(int[] nums, int target) {
        return binarySearch(nums, 0, nums.length - 1, target);
    }
    private int binarySearch(int[] nums, int lo, int hi, int target) {
        if(lo > hi) return -1;
        int mid = (lo + hi) / 2;
        return target > nums[mid] ? binarySearch(nums, mid + 1, hi, target) :
                    target < nums[mid] ? binarySearch(nums, lo, mid - 1, target) : mid;
    }
}