面试题38 数字在排序数组中出现的次数

题目描述

统计一个数字在排序数组中出现的次数。
 1 class Solution {
 2 public:
 3     int getFirstK(vector<int> data ,int k){
 4         int low = 0, high = data.size() - 1, mid;
 5         while (low <= high){
 6             mid = (low + high) / 2;
 7             if ((mid > 0 && data[mid] == k && data[mid - 1] != k) || data[mid] == k && mid == 0)
 8                 return mid;
 9             else if (data[mid] > k || data[mid - 1] == k)
10                 high = mid - 1;
11             else
12                 low = mid + 1;
13         }
14         return -1;
15     }
16     
17     int getLastK(vector<int> data ,int k){
18         int low = 0, high = data.size() - 1, mid;
19         while (low <= high){
20             mid = (low + high) / 2;
21             if ((mid < data.size() - 1 && data[mid] == k && data[mid + 1] != k) || data[mid] == k && mid == data.size() - 1)
22                 return mid;
23             else if (data[mid] < k || data[mid + 1] == k)
24                 low = mid + 1;
25             else
26                 high = mid - 1;
27         }
28         return -1;
29     }
30     
31     int GetNumberOfK(vector<int> data ,int k) {
32         int num = 0, length = data.size();
33         if (length == 0)
34             return num;
35         int first = getFirstK(data ,k);
36         int last = getLastK(data ,k); 
37         
38         if (first > -1 && last > -1)
39             num = last - first + 1;
40         return num;
41     }
42 };

 

posted @ 2016-04-06 12:34  早杰  阅读(123)  评论(0)  编辑  收藏  举报