字符串逆转

只将字符串内部逆转，比如说输入为we are girl，结果变为ew era lrig。

最初写的程序为

int main()
{
	string a;
	int beg = 0;
	int end = 0;
	getline(cin, a);
	for (int i = 0; i < a.size(); i++)
	{
		if (a[i] == ' ')
		{
			end = i-1;
			vector<char> zj;
			for (int j = end; j >= beg; j--)
			{
				char zjz;
				zjz = a[j];
				zj.push_back(zjz);
			}
			for (int j = beg; j <= end; j++)
			{
				a[j] = zj[j - beg];
			}
			beg = i + 1;
		}
		if (i == a.size()-1)
		{
			end = i;
			vector<char> zj;
			for (int j = end; j >= beg; j--)
			{
				char zjz;
				zjz = a[j];
				zj.push_back(zjz);
			}
			for (int j = beg; j <= end; j++)
			{
				a[j] = zj[j - beg];
			}
			
		}
	}
	cout << a << endl;
	while (1);
	return 0;
}

当然也可以用指针的方法啦

char* reversesetence(char *a)
{
	if (a == NULL)
		return NULL;
	char *pbegin = a;//这种方法默认指向第一个位置
	char *pend = a;
	while (*pbegin != '\0')
	{
		if (*pbegin == ' ')
		{
			pbegin++;
			pend++;
		}
		else if (*pend == ' ' || *pend == '\0')
		{
			reverseit(pbegin,--pend);
			pbegin = ++pend;
		}
		else
		{
			pend++;
		}
	}
	return a;
}
void reverseit(char* pbegin, char* pend)
{
	if (pbegin == NULL || pend == NULL)
		return;
	while (pbegin < pend)
	{
		char temp = *pbegin;
		*pbegin= *pend;
		*pend = temp;
		pbegin++, pend--;
	}
}