186.Reverse Words in a String II

    
    /*
     * 186.Reverse Words in a String II
     * 2016-6-6 by Mingyang
     * Given s = "the sky is blue",
     * return "blue is sky the".
     * Could you do it in-place without allocating extra space?
     * 这个题目是I的翻版，只是多了一个条件，能否不用额外的内存，所以我在这里先把所有string reverse一遍
     * 然后把每个词语再reverse一遍
     */
     public void reverseWords(char[] s) {
            reverse(s, 0, s.length-1);
            int start = 0;
            for(int i = 0; i< s.length; i++){
                if(s[i] == ' '){
                    reverse(s, start, i-1);
                    start = i+1;
                }
            }
            reverse(s, start, s.length-1); 
      }    
     public void reverse(char[] s, int l, int r){
            while(l < r){
                char temp = s[l];
                s[l] = s[r];
                s[r] = temp;
                l++;
                r--;
            }
      }