LeetCode Reverse Words in a String III

原题链接在这里：https://leetcode.com/problems/reverse-words-in-a-string-iii/#/description

题目：

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"

Note: In the string, each word is separated by single space and there will not be any extra space in the string.

题解：

遇到空格就把之前标记的部分reverse.

Note: 最后一次reverse别忘了.

Time Complexity: O(n), n = s.length().

Space: O(n), char array.

AC Java:

 class Solution {
     public String reverseWords(String s) {
         if(s == null || s.length() == 0){
             return s;
         }

         int len = s.length();
         char [] charArr = s.toCharArray();

         int lo = 0;
         for(int i = 0; i<=len; i++){
             if(i==len || charArr[i]==' '){
                 reverse(charArr, lo, i-1);
                 lo = i+1;
             }
         }

         return new String(charArr);
     }

     private void reverse(char [] s, int i, int j){
         while(i < j){
             swap(s, i++, j--);
         }
     }

     private void swap(char [] s, int i, int j){
         char temp = s[i];
         s[i] = s[j];
         s[j] = temp;
     }
 }

类似Reverse String II.