题解 | #翻转单词序列#

import java.util.*;
public class Solution {
    public String ReverseSentence(String str) {
        if (str.length() < 2) {
            return str;
        }
        int start = 0;
        char pre = str.charAt(0);
        Stack<String> stack = new Stack<>();
        for (int i = 0; i < str.length(); i++) {
            char currentChr = str.charAt(i);
            if ((currentChr == ' ' && pre != ' ') || (currentChr != ' ' && pre == ' ')) {
                String tmpStr = str.substring(start, i);
                stack.push(tmpStr);
                pre = currentChr;
                start = i;
            }
        }
        stack.push(str.substring(start));
        StringBuffer sb = new StringBuffer("");
        while (!stack.isEmpty()) {
            sb.append(stack.pop());
        }
        return new String(sb);
    }
}