[剑指Offer] 37.数字在排序数组中出现的次数

 1 class Solution {
 2 public:
 3     int getIndexbyDivision(vector<int> data,int k){
 4         int left = 0,right = data.size() - 1;
 5         int middle = left + (right - left)/2;
 6         while(left <= right){
 7             if(k > data[middle])
 8                 left = middle + 1;
 9             else if(k < data[middle])
10                 right = middle - 1;
11             else 
12                 return middle;
13             middle = left + (right - left)/2;
14         }
15         return -1;
16     }
17     int GetNumberOfK(vector<int> data ,int k) {
18         int index = getIndexbyDivision(data,k);
19         if(index == -1) return 0;
20         int num = 1;
21         for(int i = index - 1;i >= 0 && data[i] == k;i --)    num++;
22         for(int j = index + 1;j < data.size() && data[j] == k;j ++)    num++;
23         return num;
24     }
25 };