151. Reverse Words in a String

时间:2021-03-16 15:46:06

关键在于清除多余空格:

class Solution {
public:
    
    void reverseWords(string &s) {
        
       int begin = 0;
        for (; begin < s.size(); begin++)
            if (s[begin] != ' ')
                break;  //find the leading spaces
        s.erase(0, begin); //delete the leading spaces

        int end = s.size() - 1;
        for (; end > -1; end--)
            if (s[end] != ' ')
                break;
        s.erase(end + 1, s.size() - end);//delete the after spaces
        for (int i = 0; i < s.size(); i++)
        {
            if (s[i] == ' ')
            {
                int count = 1;
                int j = i + 1;
                while (s[j] == ' ')
                {
                    j++;
                    count++;
                }

                if (count > 1)
                    s.erase(i + 1, j - i - 1);
                i++;
            }
        } // delete tabbed spaces
        reverseSentence(s, 0, s.size()-1); //reverse the whole sentence

        reverseWord(s);
    }
    
    void reverseSentence(string &s,int begin,int end)   
    {
        while(begin<end)
        {
            char temp=s[begin];
            s[begin]=s[end];
            s[end]=temp;
            begin++;
            end--;
        }
    }
    
    void reverseWord(string &s)
    {
       int flag=0;
       for(int begin=0;begin<=s.length();begin++)
        {
            if(s[begin]==' '||s[begin]=='\0')  //find a word 
            {
                reverseSentence(s,flag,begin-1);
                flag=begin+1;
            } 
            
        }
    }
};