QUESTION:

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].

EXPLANATION:

二分查找法就不用细说了。

需要注意的是mid = start+1，mid=end-1

SOLUTION:

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