题解 | 牛群消息传递

import java.util.*;


public class Solution {
    public String reverseWords (String s) {
        // 1. split
        final char[] chars = s.toCharArray();
        final int n = chars.length;
        final Deque<String> words = new ArrayDeque<>();
        int i = 0;
        while (i < n) {
            if (chars[i] == ' ') {
                ++i;
                continue;
            }
            final int start = i;
            while (i < n && chars[i] != ' ') {
                ++i;
            }
            words.addLast(s.substring(start, i));
        }
        // 2. reverse
        final StringBuilder sb = new StringBuilder();
        sb.append(words.removeLast());
        while (!words.isEmpty()) {
            sb.append(' ');
            sb.append(words.removeLast());
        }
        return sb.toString();
    }
}