剑指Offer36 数字在排序数组中出现的次数

 /*************************************************************************
     > File Name: 36_NumberOfKey.c
     > Author: Juntaran
     > Mail: JuntaranMail@gmail.com
     > Created Time: 2016年09月03日 星期六 09时32分10秒
  ************************************************************************/

 #include <stdio.h>

 // 寻找第一个Key的下标
 int GetFirstKey(int* nums, int length, int key, int left, int right)
 {
     if (nums==NULL || length<= || left>right)
         return -;

     int middle = (left + right) / ;
     if (key == nums[middle])
     {
         if ((middle> && nums[middle-]!=key) || middle==)
             return middle;
         else
             right = middle - ;
     }
     else if (key > nums[middle])
         left = middle + ;
     else
         right = middle - ;

     return GetFirstKey(nums, length, key, left, right);
 }

 // 寻找最后一个Key的下标
 int GetLastKey(int* nums, int length, int key, int left, int right)
 {
     if (nums==NULL || length<= || left>right)
         return -;

     int middle = (left + right) / ;
     if (key == nums[middle])
     {
         if ((middle> && nums[middle+]!=key && middle<length) || middle==length-)
             return middle;
         else
             left = middle + ;
     }
     else if (key > nums[middle])
         left = middle + ;
     else
         right = middle - ;

     return GetLastKey(nums, length, key, left, right);
 }

 int GetNumberOfKey(int* nums, int length, int key)
 {
     int count = ;
     if (nums==NULL || length<=)
         return ;

     int first = GetFirstKey(nums, length, key, , length-);
     int last  = GetLastKey( nums, length, key, , length-);

     if (first>= && last>=)
         count = last - first + ;

     printf("count is %d\n", count);
     return count;
 }

 int main()
 {
     int nums[] = {, , , , , , , };
     int length = ;
     int key = ;

     GetNumberOfKey(nums, length, key);
 }