【LeetCode】 151. Reverse Words in a String 翻转字符串里的单词（Medium）（JAVA）每日一题

【LeetCode】 151. Reverse Words in a String 翻转字符串里的单词（Medium）（JAVA）

题目地址: https://leetcode.com/problems/reverse-words-in-a-string/

题目描述：

Given an input string, reverse the string word by word.

Example 1:

Input: "the sky is blue"
Output: "blue is sky the"

Example 2:

Input: "  hello world!  "
Output: "world! hello"
Explanation: Your reversed string should not contain leading or trailing spaces.

Example 3:

Input: "a good   example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.

Note:

• A word is defined as a sequence of non-space characters.
• Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
• You need to reduce multiple spaces between two words to a single space in the reversed string.

Follow up:

For C programmers, try to solve it in-place in O(1) extra space.

题目大意

给定一个字符串，逐个翻转字符串中的每个单词。

解题方法

比较简单，只要注意第一个单词后面没有空格即可

class Solution {
    public String reverseWords(String s) {
        StringBuilder sb = new StringBuilder();
        int count = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == ' ') {
                if (count > 0) {
                    if (sb.length() > 0) {
                        sb.insert(0, s.substring(i - count, i) + " ");
                    } else {
                        sb.append(s.substring(i - count, i));
                    }
                }
                count = 0;
            } else {
                count++;
            }
        }
        if (count > 0) {
            if (sb.length() > 0) {
                sb.insert(0, s.substring(s.length() - count, s.length()) + " ");
            } else {
                sb.append(s.substring(s.length() - count, s.length()));
            }
        }
        return sb.toString();
    }
}

执行用时 : 6 ms, 在所有 Java 提交中击败了 49.40% 的用户
内存消耗 : 39.4 MB, 在所有 Java 提交中击败了 5.41% 的用户