557. Reverse Words in a String III

Problem Statement

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.

Thinking

题意就是反转每个单词，主要学到了怎么反转字符数组。

Solution

class Solution {
   public  String reverseWords(String s)
    {
        char[] s1 = s.toCharArray();
        int i = 0;
        for(int j = 0; j < s1.length; j++)
        {
            if(s1[j] == ' ')
            {
                reverse(s1, i, j - 1);
                i = j + 1;
            }
        }
        reverse(s1, i, s1.length - 1);
        return new String(s1);
    }

    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--;
        }
    }
}