53-1:数字在排序数组中出现的次数

因为有序，用二分查找

class Solution {
public:
    int GetNumberOfK(vector data ,int k) {
        int down=lower_bound(data.begin(),data.end(),k)-data.begin();
        int up=upper_bound(data.begin(),data.end(),k)-data.begin();
        return up-down;
    }
};