[剑指offer]翻转句子 ； 左旋字符串

/*
42:> 翻转句子 ； 左旋字符串
i am student -> student am i (整体翻转，局部翻转)
*/

void Reserve(char* pBegin, char* pEnd)
{
if (pBegin == NULL || pEnd == NULL || pBegin+1==pEnd)
return;
while (pBegin < pEnd)
{
std::swap(*pBegin,*pEnd);
pBegin++;
pEnd--;
}
}

void ReserveSentense(char* pData)
{
if (pData == NULL)
return;
char* pBegin = pData;
char* pEnd = pBegin;
while (*pEnd != '\0')
pEnd++;
pEnd--;  //指向尾

Reserve(pBegin, pEnd);//整体翻转

pEnd = pBegin = pData;
while (*pBegin != '\0')
{
if (*pBegin == ' ')
{
pBegin++;
pEnd++;
}
else if (*pEnd == ' ' || *pEnd == '\0')
{
Reserve(pBegin, --pEnd);
pBegin = ++pEnd;
}
else
++pEnd;
}
}

//void test()
//{
//  //char ar[] = "i am a student";
//  char ar[] = "                                i am a student";
//  ReserveSentense(ar);
//  cout << ar /*<< endl*/;
//}
/*
左旋单词
abcdefg ->2 -> cdefgab
分两部分 ab cdefg
整体翻转 部分翻转
*/
void LeftRotateStr(char*pStr, int n)
{
if (pStr == NULL || n<= 0)
return;
int len = strlen(pStr);
n %= len;//大于长度会指向非法内存

char* pFirstStart = pStr;
char* pFirstEnd = pStr + n - 1;
char* pSecondStart = pStr + n;
char* pSecondEnd = pStr + len - 1;

Reserve(pFirstStart, pFirstEnd);
Reserve(pSecondStart, pSecondEnd);
Reserve(pFirstStart, pSecondEnd);
}

//void test()
//{
//  char ar[] = "i am a student";
//
//  LeftRotateStr(ar,15);
//  cout << ar << endl;
//}