LeetCode - Reverse Words in a String II

Posted 2020-11-07 IncredibleThings

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

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

Could you do it in-place without allocating extra space?

 

 

方法还是很简单，先把每个单词翻转一遍，再把整个字符串翻转一遍

    public void reverseWords(char[] s) {
        if(s == null){
            return;
        }
        int i = 0;
        for(int j=0; j<s.length; j++){
            if(s[j] == ‘ ‘){
                reverse(s, i, j-1);
                i = j+1;
            }
        }
        reverse(s, i, s.length-1);
        reverse(s, 0, s.length-1);
    }
    
    public void reverse(char[] s, int left, int right){
        if(s == null || s.length == 0){
            return;
        }
        while(left < right){
            char temp = s[left];
            s[left] = s[right];
            s[right] = temp;
            left ++;
            right --;
        }
    }