[英](Java) Need to reverse a string sentence using stack
給定一個完整的句子,是否可以在不反轉單詞本身的情況下反轉堆棧。 即最初的句子 - 瑪麗有一只小羊羔。 它的羊毛潔白如雪。 新句子——小羊羔有瑪麗。 雪白如羊毛。 基本上卡在循環部分。 出於某種原因,我讓它顯示單詞並在期間中斷,但對於我的生活,我似乎無法讓 push/pop args 做我希望他們做的事情。 我把所有的評論都寫下來了,因為當我從編碼中休息一下時,它可以幫助我整理我的想法,就像我現在正在做的那樣,然后在我的電腦上打斷我的頭。
public class ReverseTheStack
{
private static LinkedList<Object> list = new LinkedList<Object>();
public static class Stack
{
public void push(Object obj)
{
list .addFirst(obj);
}
public Object pop()
{
return list.removeFirst();
}
}
public static void main(String [] args)
{
//First hard code the sentence for testing
String sentence = "Mary had a little lamb. Its fleece was white as snow.";
//The scanner is created with the String obj inside it
Scanner in = new Scanner(sentence);
//Set the scanner's delimiter to a period and the space after: "\\. "
in.useDelimiter(" ");
//Create a stack
Stack sentenceReversal = new Stack();
while(in.hasNext())
{
sentenceReversal.push(in.next());
if(in.toString().contains("\\."))
{
System.out.println(sentenceReversal.pop());
}
}
//Close the scanner
in.close();
}
}
可以使用自 Java 1.0 以來存在的Stack
實現(盡管即使提到的 Javadoc 頁面也建議使用Deque
接口及其實現提供更豐富的 LIFO 操作集):
String str = "Mary had a little lamb. Its fleece was white as snow.";
Stack<String> stack = new Stack<>();
StringBuilder sb = new StringBuilder(); // build result string
// splitting text into sentences
for (String sentence : str.split("\\.\\s*")) {
stack.clear();
// splitting into words
for (String word : sentence.split("\\s+")) {
stack.push(word.toLowerCase()); // fix letter case
}
boolean first = true;
while (!stack.empty()) {
String word = stack.pop();
if (first) {
// capitalize the first letter in the reversed sentence
first = false;
word = word.substring(0, 1).toUpperCase() + word.substring(1);
}
if (sb.length() > 0) {
sb.append(' ');
}
sb.append(word);
}
sb.append('.');
}
System.out.println(sb);
輸出:
Lamb little a had mary. Snow as white was fleece its.
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