zoukankan      html  css  js  c++  java
  • 284. Peeking Iterator

    Given an Iterator class interface with methods: next() and hasNext(), design and implement a PeekingIterator that support the peek() operation -- it essentially peek() at the element that will be returned by the next call to next().

    Example:

    Assume that the iterator is initialized to the beginning of the list: [1,2,3].
    
    Call next() gets you 1, the first element in the list.
    Now you call peek() and it returns 2, the next element. Calling next() after that still return 2. 
    You call next() the final time and it returns 3, the last element. 
    Calling hasNext() after that should return false.
    

    Follow up: How would you extend your design to be generic and work with all types, not just integer?

    // Java Iterator interface reference:
    // https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
    class PeekingIterator implements Iterator<Integer> {  
        private Integer next = null;
        private Iterator<Integer> iter;
    
        public PeekingIterator(Iterator<Integer> iterator) {
            // initialize any member here.
            iter = iterator;
            if (iter.hasNext())
                next = iter.next();
        }
        
        // Returns the next element in the iteration without advancing the iterator. 
        public Integer peek() {
            return next; 
        }
    
        // hasNext() and next() should behave the same as in the Iterator interface.
        // Override them if needed.
        @Override
        public Integer next() {
            Integer res = next;
            next = iter.hasNext() ? iter.next() : null;
            return res; 
        }
    
        @Override
        public boolean hasNext() {
            return next != null;
        }
    }
  • 相关阅读:
    hiveserver2 with kerberos authentication
    python Basic usage
    python Quicksort demo
    Python HeapSort
    mrunit for wordcount demo
    CCDH证书
    Hadoop question list
    Hadoop Yarn core concepts
    Hadoop Resource
    Hadoop could not find or load main class
  • 原文地址:https://www.cnblogs.com/wentiliangkaihua/p/11921200.html
Copyright © 2011-2022 走看看