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<=0 || left>right)
        return -1;
    
    int middle = (left + right) / 2;
    if (key == nums[middle])
    {
        if ((middle>0 && nums[middle-1]!=key) || middle==0)
            return middle;
        else
            right = middle - 1;
    }
    else if (key > nums[middle])
        left = middle + 1;
    else
        right = middle - 1;
    
    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<=0 || left>right)
        return -1;
    
    int middle = (left + right) / 2;
    if (key == nums[middle])
    {
        if ((middle>0 && nums[middle+1]!=key && middle<length) || middle==length-1)
            return middle;
        else
            left = middle + 1;
    }
    else if (key > nums[middle])
        left = middle + 1;
    else
        right = middle - 1;
    
    return GetLastKey(nums, length, key, left, right);
}

int GetNumberOfKey(int* nums, int length, int key)
{
    int count = 0;
    if (nums==NULL || length<=0)
        return 0;
    
    int first = GetFirstKey(nums, length, key, 0, length-1);
    int last  = GetLastKey( nums, length, key, 0, length-1);
    
    if (first>=0 && last>=0)
        count = last - first + 1;
    
    printf("count is %d
", count);
    return count;
}

int main()
{
    int nums[] = {1, 2, 3, 3, 3, 3, 4, 5};
    int length = 8;
    int key = 3;
    
    GetNumberOfKey(nums, length, key);
}