Question

给定一个IntegerIterator（实现hasNext，next，remove），实现具有hasNext，next，remove
的PositiveIterator

有人能为这个问题提出一些想法吗？这不是家庭作业！

例如：

int[] a = new int[]{1,-2,-3,4,5,-6,7,-8,9};
IntegerIterator it = new IntegerIterator(a);
PositiveIterator iter = new PositiveIterator(it);
Console.WriteLine(iter.HasNext()); //true
Console.WriteLine(iter.HasNext()); //true
Console.WriteLine(iter.HasNext()); //true
Console.WriteLine(iter.Next()); //1
Console.WriteLine(iter.Next()); //4
Console.WriteLine(iter.Next()); //5

Answer 1

PositiveIterator.Next不应该成为问题。只需致电Iterator.Next，直到价值为正。 PositiveIterator.Remove只需要拨打Iterator.Remove。 PositiveIterator.HasNext是代码有点难看的原因，因为给定的方法只允许单向迭代。

class PositiveIterator:
    int next = -1 //holds the next value to return
    IntegerIterator iter //the integeriterator wrapped by this object

    PositiveIterator(IntegerIterator it)
        iter = it

        //search for the first positive value for next
        while iter.HasNext() AND ((next = iter.Next()) < 1)
            NOOP

    HasNext()
        return next != -1

    Next()
        //the current value to return
        int tmp = next

        //search for the next positive value
        while iter.HasNext() AND ((next = iter.Next()) < 1)
            NOOP

        if NOT iter.HasNext()
            next = -1 //no next positive value available

        return tmp

     Remove()
         if next == -1
             return

         iter.Remove()

         //update the next value
         next = Next()

基本上PositiveInteger需要预测接下来要返回的值的值。

Answer 2

这非常简单 - 覆盖构造函数，HashNext()和Next()方法，这样你就可以随时使用＆＃34;＆＃34;下一个正值，同时跳过所有负值。

伪代码：

class PositiveIterator:
    private int next = -1;
    private final Integer i;
    PositiveIterator(Itertor i):
          while (i.HashNext() && (next = i.Next()) <= 0) ;
          //at this point next holds the next positive element, if such exists
          this.i = i;
    boolean HasNext():
         return (next > 0)
    int Next():
         int tempVal = -1;
         while (i.HashNext() && (tempVal = i.Next()) <= 0) ;
         int res = next;
         next = tempVal;
         return next;

请注意，在任何方法中，任何方法 - next > 0当且仅当数组中还有一些正元素，并且它将保存您需要生成的下一个元素。

给定整数迭代器的正迭代器设计

2 个答案: