class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
     *
     * 
     * @param nums int整型vector 
     * @param target int整型 
     * @return int整型
     */
    int search(vector<int>& nums, int target) {
        // write code here
        if(nums.size()==0)
            return -1;
        int left =0;int right=nums.size()-1;
        while(left<=right)
        {
            int mid=left+(right-left)/2;
            if(nums[mid]<target)
                left=mid+1;
            else
                right=mid-1;
            //确保left左边的元素都小于target,right右边的元素都大于等于target
        }
    if(nums[left]==target)
        return left;
    return -1;
    }
};