557.Reverse-Words-in-a-String-III

557. Reverse Words in a String III

题目地址

题目描述

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.

代码

Approach 1:

public class Solution {
public String reverseWords(String s) {
String words[] = s.split(" ");
StringBuilder res = new StringBuilder();
for (String word: words) {
res.append(new StringBuffer(word).reverse().toString() + " ");
}
return res.toString().trim();
}
}

Approach #2 Without using pre-defined split and reverse function

public class Solution {
public String reverseWords(String s) {
String words[] = split(s);
StringBuilder res = new StringBuilder();
for (String word: words)
res.append(reverse(word) + " ");
return res.toString().trim();
}
public String[] split(String s) {
ArrayList <String> words = new ArrayList <> ();
StringBuilder word = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == ' ') {
words.add(word.toString());
word = new StringBuilder();
} else {
word.append(s.charAt(i));
}
}
words.add(word.toString());
return words.toArray(new String[words.size()]);
}
public String reverse(String s) {
StringBuilder res = new StringBuilder();
for (int i = 0; i < s.length(); i++)
res.insert(0, s.charAt(i));
return res.toString();
}
}

Approach #3 Using StringBuilder and reverse method

public class Solution {
public String reverseWords(String input) {
final StringBuilder result = new StringBuilder();
final StringBuilder word = new StringBuilder();
for (int i = 0; i < input.length(); i++) {
if (input.charAt(i) != ' ') {
word.append(input.charAt(i));
} else {
result.append(word.reverse());
result.append(" ");
word.setLength(0);
}
}
result.append(word.reverse());
return result.toString();
}
}