字符串按word反转

方法一、不用栈

void reverseChar(char* str, int len)
{
	char* q = str+len-1;
	char* p = str;

	if (!len)
		return;

	while( p<q )
	{
		char tmp = *p;
		*p = *q;
		*q = tmp;
		p++;
		q--;
	}

	for (int i=0; i<len; i++)
		cout << str[i];
	cout << endl;
}

void reverseWord(char* str)
{
	char* p = str;
	int count = 0;
	int total = 0;

	while(1)
	{
		p++;
		count++;
		total++;

		if ( *p==' ' || *p=='\0' )
		{
			reverseChar(p-count, count);
			//note that, it is -1,not 0
			count=-1;
			
			if ( *p=='\0' )
			{
				break;
			}
		}
	}

	reverseChar(str, total);
}

方法二、采用了两个stack，一个用于整个字符串的反转，一个用于保证word内部顺序不变。

char* reverse_word(char* str)
{
    stack<char> st;
    stack<char> word;
  
    char* p = str;
  
    st.push('\0');
    while( *p != '\0')
    {
        while( *p == ' ')
            st.push(*p++);
  
        if ( *p == '\0')
            break;
  
        while( *p != '\0' && *p != ' ')
            word.push(*p++);
  
        while( !word.empty() )
        {
            st.push( word.top() );
            word.pop();
        }
    }
  
    p = str;
    while( *p != '\0' )
    {
        *p = st.top();
        st.pop();
        p++;
    }
  
    return str;
}
 