剑指offer——面试题42：翻转单词顺序VS左旋转字符串

void Reverse(char *pBegin, char *pEnd)
{
    if(pBegin == NULL || pEnd == NULL)
        return;

    while(pBegin < pEnd)
    {
        char temp = *pBegin;
        *pBegin = *pEnd;
        *pEnd = temp;

        pBegin ++, pEnd --;
    }
}

char* ReverseSentence(char *pData)
{
    if(pData == NULL)
        return NULL;

    char *pBegin = pData;

    char *pEnd = pData;
    while(*pEnd != '\0')
        pEnd ++;
    pEnd--;

    // 翻转整个句子
    Reverse(pBegin, pEnd);

    // 翻转句子中的每个单词
    pBegin = pEnd = pData;
    while(*pBegin != '\0')
    {
        if(*pBegin == ' ')
        {
            pBegin ++;
            pEnd ++;
        }
        else if(*pEnd == ' ' || *pEnd == '\0')
        {
            Reverse(pBegin, --pEnd);
            pBegin = ++pEnd;
        }
        else
        {
            pEnd ++;
        }
    }

    return pData;
}

char* LeftRotateString(char* pStr, int n)
{
    if(pStr != NULL)
    {
        int nLength = static_cast<int>(strlen(pStr));
        if(nLength > 0 && n > 0 && n < nLength)
        {
            char* pFirstStart = pStr;
            char* pFirstEnd = pStr + n - 1;
            char* pSecondStart = pStr + n;
            char* pSecondEnd = pStr + nLength - 1;

            // 翻转字符串的前面n个字符
            Reverse(pFirstStart, pFirstEnd);
            // 翻转字符串的后面部分
            Reverse(pSecondStart, pSecondEnd);
            // 翻转整个字符串
            Reverse(pFirstStart, pSecondEnd);
        }
    }

    return pStr;
}