剑指offer题解汇总 Java实现

https://blog.csdn.net/guliguliguliguli/article/details/126089434

本题链接

https://www.nowcoder.com/exam/oj/ta?page=1&tpId=13&type=13

题目

思路 & 代码

方案一 数组

按照" "将字符串分割，然后从数组的最后一个开始输出，全部添加到stringbuilder中

注意：空格的添加

import java.util.*;

public class Solution {
    public String ReverseSentence(String str) {
        if (str.length() == 0) {
            return str;
        }
        String[] res = str.split(" ");
        StringBuilder builder = new StringBuilder();
        for (int i = res.length - 1; i >= 0; i--) {
            if (i == 0) {
                builder.append(res[i]);
            } else {
                builder.append(res[i]).append(" ");
            }
        }
        return builder.toString();
    }
}

方案二 栈

栈具有先进后出的特点，将按照" "分割以后的结果依次添加到栈中，注意在添加数组元素时，也要添加" "

import java.util.*;

public class Solution {
    public String ReverseSentence(String str) {
        if (str.length() == 0) {
            return str;
        }
        String[] res = str.split(" ");

        Stack<String> stack = new Stack<>();

        for (String s : res) {
            stack.push(s);
            stack.push(" ");
        }

        //去掉最后一个空格
        stack.pop();

        StringBuilder builder = new StringBuilder();

        while (!stack.isEmpty()) {
            builder.append(stack.pop());
        }

        return builder.toString();

    }
}