二分查找法

class Solution {

    public int search(int[] nums, int target) {
        //定义左边界、右边界
        int left=0;
        int right=nums.length-1;
        
        while(left<=right){
            int mid=left+(right-left+1)/2;
            if(nums[mid]==target){
                return mid;
            }else if(nums[mid]>target){
                right=mid-1;
            }else if(nums[mid]<target){
                left=mid+1;
            }
        }
        return -1;
    }
}