创建唯一元素的链接列表

Question

我有一个学校作业，我需要在 Java 中使用列表并从文本文件中插入单词，并排除类似的单词。我正在尝试这样做，以便仅在不等于现有元素的情况下将新元素添加到列表中，但无论如何它都会不断添加元素。

我在类 List 中按字母顺序插入新元素的方法

public void inserirOrdem( String elemento ) {
        No novoNo = new No( elemento );
        No actual = cabeca;  //actual=head of the list
        No anterior = null;
        // look for place where to add new element
        while( actual != null && actual.item.compareTo( elemento ) < 0 ) {
        anterior = actual;
        actual = actual.prox;
        }
        if(!elemento.equals(actual.item)) { //so that the new element won't be added if there's an equal one.... doesn't work
        novoNo.prox = actual;
        if( anterior == null ) //in case the list doesn't have any elements
        cabeca = novoNo;
        else
        anterior.prox = novoNo;
        nElementos++;
        }
}

我的节点类：

private class No{
    No prox;
    String item;
    No( String elemento ) {
        item = elemento; 
        prox = null; 
    }
}

Answer 1

您可以使用 Set 集合。它不允许任何已经等于集合中的新元素。只需要在 No 类中实现 equals 方法。

请参阅此处和此处，但谷歌中有很多示例。

干杯。

Answer 2

这是一个可行的解决方案，尽管我建议进一步测试它。我没有您原来的LList类，所以我使用的是静态版本，该版本应该可以轻松适应您的需求。

class Main {
    /* Inserts a node into a unique, alphabetical list */
    public static No inserirOrdem(No cabeca, String elemento) {
          if (elemento == null) { return cabeca; }
          if (cabeca == null) { return new No(elemento); }
          No novoNo = new No(elemento);
          No actual = cabeca;
          No anterior = null;
          // valid entry to add at beginning of list
          if (cabeca.item.compareTo(elemento) > 0) {
              novoNo.prox = cabeca;
              return novoNo;
          }
          while (actual != null && actual.item.compareTo(elemento) < 0) {
              anterior = actual;
              actual = actual.prox;
          }
          // valid entry to add at end of list
          if (actual == null) { 
              anterior.prox = novoNo;
              return cabeca;
          }
          // valid entry to add in middle of list
          if (actual.item.compareTo(elemento) > 0) { 
              if (anterior == null) {
                  cabeca = novoNo;
              }
              else {
                  anterior.prox = novoNo;
                  novoNo.prox = actual;
              }
          }
          return cabeca;
    }
    /* Prints a linked list */
    public static void p(No head) {
        No c = head;
        while (c != null) {
            System.out.print(c.item + " -> ");
            c = c.prox;
        }
        System.out.println("n");
    }
    public static void main(String[] args) {
        No head = new No("a");
        No b = new No("b");
        No d = new No("d");
        No e = new No("e");
        head.prox = b;
        b.prox = d;
        d.prox = e;
        System.out.println("Original:");
        p(head);
        System.out.println("Try to add duplicates:");
        head = inserirOrdem(head, "a");
        head = inserirOrdem(head, "b");
        head = inserirOrdem(head, "d");
        p(head);
        System.out.println("Try to add c in the middle:");
        head = inserirOrdem(head, "c");
        p(head);
        System.out.println("Try to add f at the end:");
        head = inserirOrdem(head, "f");
        p(head);
        System.out.println("Try to add h at the end:");
        head = inserirOrdem(head, "h");
        p(head);
        System.out.println("Try to add g in the middle:");
        head = inserirOrdem(head, "g");
        p(head);
        head = null;
        System.out.println("Null head, add a:");
        head = inserirOrdem(head, "a");
        p(head);
        System.out.println("Try to add null str:");
        head = inserirOrdem(head, null);
        p(head);
        head = new No("c");
        System.out.println("Try to add duplicate:");
        head = inserirOrdem(head, "c");
        p(head);
        System.out.println("Try to add a at beginning of list:");
        head = inserirOrdem(head, "a");
        p(head);
        System.out.println("Try to add z at end of list:");
        head = inserirOrdem(head, "z");
        p(head);
        System.out.println("Try to add f at middle of list:");
        head = inserirOrdem(head, "f");
        p(head);
    }
}
class No {
    No prox;
    String item;
    No (String elemento) {
        item = elemento;
        prox = null;
    }
}

输出：

Java 版本 "1.8.0_31"Java(TM( SE 运行时环境(内部版本 1.8.0_31-b13(Java HotSpot(TM( 64-bit Server VM(build 25.31-b07，混合模式(源语言：a -> b -> d -> e ->尝试添加重复项：a -> b -> d -> e ->尝试在中间添加 c：a -> b -> c -> d -> e ->尝试在末尾添加 f：a -> b -> c -> d -> e -> f ->尝试在末尾添加 h：a -> b -> c -> d -> e -> f -> h ->尝试在中间添加 g：a -> b -> c -> d -> e -> f -> g -> h ->空头，添加：a ->尝试添加空 str：a ->尝试添加重复项：c ->尝试在列表开头添加一个：a -> c ->尝试在列表末尾添加 z：a -> c -> z ->尝试在列表中间添加 f：a -> c -> f -> z ->