题解 | #数字在升序数组中出现的次数#

1.二分法；
class Solution {
public:
int GetNumberOfK(vector<int> data ,int k) {
int len=data.size(),l=0,r=len-1,ans=0;</int>

    while(l<=r)
    {
        int mid=l+(r-l)/2;
        if(data[mid]<k)
        {
            l=mid+1;
        }
        else if(data[mid]>k)
        {
            r=mid-1;
        }
        else{
            int a=mid-1;
            int b=mid+1;
            ans++;
            while(a>=0&&data[a]==k) 
            {
                ans++;
                a--;
            }
            while(b<=r&&data[b]==k)
            {
                ans++;
                b++;
            }
            break;
        }
    }
    return ans;
}

};