leetcode 704. Binary Search （二分搜索）

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.

Example 1:

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

二分搜索target，返回index，找不到的话返回-1

思路：
一般的二分搜索法

    public int search(int[] nums, int target) {
        if(nums == null) return -1;
        int n = nums.length;
        int left = 0;
        int right = n - 1;
        
        while(left <= right) {
            int mid = left + (right - left) / 2;
            if(nums[mid] == target) {
                return mid;
            } else if (nums[mid] < target) {
                left = mid + 1;
            } else {
                right = mid - 1;
            }
        }
        return -1;
    }