私以为很简明的二分hhh

class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        int l = 0, r = nums.size() - 1;
        int cnt = 0;
        while (l <= r) {
            int m = l + (r - l) / 2;
            if (nums[m] == k) {
                cnt++;
                for(int i = m - 1; i >= l; i--)
                    if (nums[i] == k) cnt++;
                    else break;
                for (int j = m + 1; j <= r; j++)
                    if (nums[j] == k) cnt++;
                    else break;
                break;
            }
            else if (nums[m] < k) l = m + 1;
            else r = m - 1;
        }
        return cnt;
    }
};