ACWING67. Digital number occurring in the sorted array (wins the offer, two points)

Count the number of times a number that appears in the sort array.

E.g. input sorted array [1, 2, 3, 3, 3, 3, 4, 5], and the number 3, because 3 occurs four times in the array, the output 4.

Sample
input: [1, 2, 3, 3, 3, 3, 4, 5], 3

Output: 4

class Solution {
public:
    int LowerBound(vector<int>& nums,int k) {
        int l = 0,r = nums.size() - 1;
        int ans = 0;
        while(l <= r) {
            int mid = (l + r) >> 1;
            if(nums[mid] >= k) {
                r = mid - 1;
                ans = mid;
            }
            else l = mid + 1;
        }
    }
    
    int UpperBound(vector<int>& nums,int k) {
        int l = 0,r = nums.size() - 1;
        int ans = 0;
        while(l <= r) {
            int mid = (l + r) >> 1;
            if(nums[mid] <= k) {
                l = mid + 1;
                ans = mid;
            }
            else r = mid - 1;
        }
    }
    
    int getNumberOfK(vector<int>& nums , int k) {
        if(!nums.size()) return 0;
        int k1 = LowerBound(nums,k);
        int k2 = UpperBound(nums,k);
        return k2 - k1;
    }
};