剑指offer面试题38：数字在排序数组中出现的次数

#include "iostream"
using namespace std;
int GetFirstK(int *data, int length,int k, int start,int end)
{
if (start > end)
return -1;
int middleIndex = (start + end) / 2;
int middleData = data[middleIndex];
if (middleData == k)
{
if ((middleIndex > 0 && data[middleIndex - 1] != k)
|| middleIndex == 0)
return middleIndex;
else
end = middleIndex - 1;
}
else if (middleData > k)
end = middleIndex - 1;
else
start = middleIndex + 1;
return GetFirstK(data, length, k, start, end);
}
int GetLastK(int *data, int length, int k, int start, int end)
{
if (start > end)
return -1;
int middleIndex = (start + end) / 2;
int middleData = data[middleIndex];
if (middleData == k)
{
if ((middleIndex < length-1 && data[middleIndex + 1] != k)
|| middleIndex == length-1)
return middleIndex;
else
start = middleIndex +1;
}
else if (middleData< k)
start = middleIndex +1;
else
end = middleIndex - 1;
return GetLastK(data, length, k, start, end);
}
int GetNumberOfK(int *data, int length, int k)
{
int number = 0;
if (data!=NULL &&length>0)
{
int first = GetFirstK(data, length, k, 0, length-1);
int last = GetLastK(data, length, k, 0, length - 1);
if (first > -1 && last > -1)
number = last - first + 1;
}
return number;
}
int main()
{
int a[] = { 2,3,4,5,5,5,5,6,7,8 };
cout << GetNumberOfK(a, 10, 5);
system("pause");
return 0;
}