1 /*************************************************************************
2 > File Name: 36_NumberOfKey.c
3 > Author: Juntaran
4 > Mail: JuntaranMail@gmail.com
5 > Created Time: 2016年09月03日 星期六 09时32分10秒
6 ************************************************************************/
7
8 #include <stdio.h>
9
10 // 寻找第一个Key的下标
11 int GetFirstKey(int* nums, int length, int key, int left, int right)
12 {
13 if (nums==NULL || length<=0 || left>right)
14 return -1;
15
16 int middle = (left + right) / 2;
17 if (key == nums[middle])
18 {
19 if ((middle>0 && nums[middle-1]!=key) || middle==0)
20 return middle;
21 else
22 right = middle - 1;
23 }
24 else if (key > nums[middle])
25 left = middle + 1;
26 else
27 right = middle - 1;
28
29 return GetFirstKey(nums, length, key, left, right);
30 }
31
32 // 寻找最后一个Key的下标
33 int GetLastKey(int* nums, int length, int key, int left, int right)
34 {
35 if (nums==NULL || length<=0 || left>right)
36 return -1;
37
38 int middle = (left + right) / 2;
39 if (key == nums[middle])
40 {
41 if ((middle>0 && nums[middle+1]!=key && middle<length) || middle==length-1)
42 return middle;
43 else
44 left = middle + 1;
45 }
46 else if (key > nums[middle])
47 left = middle + 1;
48 else
49 right = middle - 1;
50
51 return GetLastKey(nums, length, key, left, right);
52 }
53
54 int GetNumberOfKey(int* nums, int length, int key)
55 {
56 int count = 0;
57 if (nums==NULL || length<=0)
58 return 0;
59
60 int first = GetFirstKey(nums, length, key, 0, length-1);
61 int last = GetLastKey( nums, length, key, 0, length-1);
62
63 if (first>=0 && last>=0)
64 count = last - first + 1;
65
66 printf("count is %d
", count);
67 return count;
68 }
69
70 int main()
71 {
72 int nums[] = {1, 2, 3, 3, 3, 3, 4, 5};
73 int length = 8;
74 int key = 3;
75
76 GetNumberOfKey(nums, length, key);
77 }
