【Lintcode】1173. Reverse Words in a String III

题目地址：

https://www.lintcode.com/problem/reverse-words-in-a-string-iii/description

给定一个字符串$s$，其包含单词以及空格（以空格分开的都看作单词）。要求将每个单词翻转，但要保持单词之间原来的顺序。

代码如下：

public class Solution {
    /**
     * @param s: a string
     * @return: reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order
     */
    public String reverseWords(String s) {
        // Write your code here
        char[] str = s.toCharArray();
        for (int i = 0, j = 0; i <= str.length; i++) {
        	// 最后一部分别忘了翻转
            if (i == str.length || str[i] == ' ') {
                reverse(str, j, i - 1);
                j = i + 1;
            }
        }
        
        return new String(str);
    }
    
    private void reverse(char[] s, int i, int j) {
        for (; i < j; i++, j--) {
            char tmp = s[i];
            s[i] = s[j];
            s[j] = tmp;
        }
    }
}

时间复杂度$O(l_s)$，空间$O(1)$。