剑指offer——面试题38：数字在排序数组中出现的次数

来源：互联网发布：阿里云域名解析a记录编辑：程序博客网时间：2024/04/27 20:20

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;}

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