Java使用堆栈来反转句子中的单词
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Java Using a stack to reverse the words in a sentence
提问by user3071909
I am supposed to write a code that reads a sentence from the user and prints the characters of the words in the sentence backwards. It should include a helper method that takes a String as a parameter and returns a new String with the characters reversed. The individual words are reversed, for example the sentence "Hi dog cat". would print "iH god tac". I can make the entire sentence reverse but i cant figure out how to reverse individual words. Thanks! Also, i know how to return the String once i have found it, but i just cant get the right string
我应该编写一个代码，从用户那里读取一个句子，然后向后打印句子中单词的字符。它应该包含一个辅助方法，该方法将字符串作为参数并返回一个字符颠倒的新字符串。单个单词被颠倒，例如句子“Hi dog cat”。会打印“iH God tac”。我可以将整个句子颠倒，但我无法弄清楚如何颠倒单个单词。谢谢！另外，我知道如何在找到字符串后返回它，但我就是无法获得正确的字符串
import java.util.Scanner;
import java.util.Stack;
public class ReverseStack
{
public static void main(String[] args)
{
String sentence;
System.out.println("Enter a sentence: ");
Scanner scan = new Scanner(System.in);
sentence = scan.nextLine();
String k = PrintStack(sentence);
}
private static String PrintStack(String sentence)
{
String reverse;
String stringReversed = "";
Stack<String> stack= new Stack<String>();
sentence.split(" ");
for(int i=0;i<sentence.length(); i++)
{
stack.push(sentence.substring(i, i+1));
}
while(!stack.isEmpty())
{
stringReversed += stack.pop();
}
System.out.println("Reverse is: " + stringReversed);
return reverse;
}
}
回答by hcps-tenembasj
I will type an expatiation so you can still get the experience of writing the code, rather than me just giving you the code.
我会输入一个解释，这样你仍然可以获得编写代码的经验，而不是我只是给你代码。
First create a Stackof Characters. Then use add each character in the Stringto the Stack, starting with the first char, then the second, and so on. Now either clear the Stringor create a new Stringto store the reversed word. Finally, add each character from the Stackto the String. This will pull the last character off first, then the second to last, and so on.
首先创建一个Stack的Character秒。然后使用将 中的每个字符添加String到 中Stack，从第一个开始char，然后是第二个，依此类推。现在清除String或创建一个新的String来存储反向单词。最后，添加从Stack到 的每个字符String。这将首先拉下最后一个字符，然后是倒数第二个，依此类推。
Note: I believe you have to use the Characterwrapper class, rather than the primitive char; I may be incorrect about that though.
注意：我相信你必须使用Character包装类，而不是原始的char；不过我可能是不正确的。
If you aren't familiar with how Stacks work, here is a nice interactive tool to visualize it: http://www.cise.ufl.edu/~sahni/dsaaj/JavaVersions/Stacks/AbstractStack/AbstractStack.htm
如果您不熟悉Stacks 的工作方式，这里有一个很好的交互式工具来可视化它：http: //www.cise.ufl.edu/~sahni/dsaaj/JavaVersions/Stacks/AbstractStack/AbstractStack.htm
回答by wulfgarpro
Change:
改变：
Stack<String> stack = new Stack<String>();
to be
成为
Stack<Character> stack = new Stack<Character>();
and refactor your methods code as necessary; i.e.
并根据需要重构您的方法代码；IE
What is the easiest/best/most correct way to iterate through the characters of a string in Java?
回答by Elliott Frisch
I did it with a different kind of stack, but I suspect this might help
我用不同类型的堆栈做了它，但我怀疑这可能会有所帮助
private static String reverseWord(String in) {
if (in.length() < 2) {
return in;
}
return reverseWord(in.substring(1)) + in.substring(0, 1);
}
private static String reverseSentence(String in) {
StringBuilder sb = new StringBuilder();
StringTokenizer st = new StringTokenizer(in);
while (st.hasMoreTokens()) {
if (sb.length() > 0)
sb.append(' ');
sb.append(reverseWord(st.nextToken()));
}
return sb.toString();
}
public static void main(String[] args) {
String sentence = "Hi dog cat";
String expectedOutput = "iH god tac";
System.out.println(expectedOutput
.equals(reverseSentence(sentence)));
}
Outputs
输出
true
