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reverse word in a string(leetcode)

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

click to show clarification.

Clarification:

  • What constitutes a word?
    A sequence of non-space characters constitutes a word.
  • Could the input string contain leading or trailing spaces?
    Yes. However, your reversed string should not contain leading or trailing spaces.
  • How about multiple spaces between two words?
    Reduce them to a single space in the reversed string.
  • 方法就是先將整個string翻轉,然後再將多餘空格變為一個空格,在將其中每個單詞翻轉即可。
  • 我為了避免調整空格的繁瑣移動操作,就直接另建一string,保留每個word的翻轉結果,最後將其賦值給s即可
    class Solution {
    public:
        void reverseWords(string &s) {
            if( s.empty() )
    			{ return; }
    			reverse( s.begin(),s.end() );
    			string::iterator left = s.begin(),right = s.begin();
    			enum{ OFF,ON } state;
    			state = OFF;
    			string s1;
    			for( string::iterator i = s.begin();i != s.end();i++ )	{
    				if( *i != ' ' )	{	
    					if( !state )	{
    						left = i;
    						state = ON;
    					}
    				}
    				else if( *i == ' ' )	{
    					if( state )	{
    						right = i;
    						s1 += reverse( left,right ) + ' ';
    						state = OFF;
    					}
    				}
    			}
    			if( s[s.size() - 1] != ' ')
    			    s1 += reverse( left,s.end() );
    			if( s1[s1.size() - 1] == ' ')
    			    s1.erase( s1.end() - 1 );
    			s = s1;
    	}
    	string reverse( string::iterator left,string::iterator right )	{
    			char c;
    			for( string::iterator it1 = left,it2 = right - 1;it1 < it2;it1++,it2-- )	{
    				c = *it1;
    				*it1 = *it2;
    				*it2 = c;
    			}
    			string str( left,right );
    			return str;
    		}
    };