leetcode-34：在排序数组中查找元素的第一个和最后一个位置

输入：nums = [5,7,7,8,8,10], target = 8
输出：[3,4]

输入：nums = [5,7,7,8,8,10], target = 6
输出：[-1,-1]

输入：nums = [], target = 0
输出：[-1,-1]

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        if(nums.empty()) return {-1,-1};
        vector<int> res(2,-1);
        int left=0,right=nums.size()-1;
        while(left<right){
            int mid=(left+right)/2;
            if(nums[mid]>=target){
                right=mid;
            }else{
                left=mid+1;
            }
        }
        if(nums[left]!=target) return {-1,-1};
        res[0]=left;
        left=0,right=nums.size()-1;
        while(left<right){
            int mid=(left+right+1)/2;
            if(nums[mid]<=target){
                left=mid;
            }else{
                right=mid-1;
            }
        }
        res[1]=left;
        return res;
    }
};