Search for a Range

方法：使用逼近的方法，先寻找左边边界，再找右边界，这与二分查找中边界的更新顺序相关

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        vector<int> result = {-1, -1};
        
        int ll=0, lr=nums.size()-1;
        while(ll <= lr)
        {
            int mid = (ll+lr)/2;
            if(nums[mid] < target)
                ll = mid + 1;
            else
                lr = mid - 1;
        }
        
        int rl = 0, rr = nums.size()-1;
        while(rl <= rr)
        {
            int mid = (rl + rr) / 2;
            if(nums[mid] > target)
                rr = mid - 1;
            else
                rl = mid + 1;
        }
        
        if(ll <= rr)
        {
            result[0] = ll;
            result[1] = rr;
        }
        
        return result;
    }
};

或者直接找到一个值后左右逼近即可。