题解 | #数字在升序数组中出现的次数#

用二分法分别找k-0.5和k+0.5应该插入的位置，位置距离即k的个数

class Solution {
public:    
	int bSearch(const vector<int> &vec, double k)
	{
		int beg = 0;
		int end = vec.size() - 1;
		while (beg <= end)
		{
			int mid = (beg + end);
			
			if (k < vec[mid])
			{
				end = mid - 1;
			}
			else
			{
				beg = mid + 1;
			}
		}
		
		return beg;
	}
	
    int GetNumberOfK(vector<int> vec ,int k) {
        int start = bSearch(vec, k - 0.5);
        int end = bSearch(vec, k + 0.5);
        cout << start << "," << end << endl;
		return end - start;
    }
};