LeetCode 284. Peeking Iterator

Posted 2021-02-18 Shendu.cc

题目

再维护一个iterator ，用来实现peek

/*
 * Below is the interface for Iterator, which is already defined for you.
 * **DO NOT** modify the interface for Iterator.
 *
 *  class Iterator {
 *		struct Data;
 * 		Data* data;
 *		Iterator(const vector<int>& nums);
 * 		Iterator(const Iterator& iter);
 *
 * 		// Returns the next element in the iteration.
 *		int next();
 *
 *		// Returns true if the iteration has more elements.
 *		bool hasNext() const;
 *	};
 */

class PeekingIterator : public Iterator {
public:
    Iterator* iter;
    int _next;
	PeekingIterator(const vector<int>& nums) : Iterator(nums) {
	    // Initialize any member here.
	    // **DO NOT** save a copy of nums and manipulate it directly.
	    // You should only use the Iterator interface methods.
        iter = new Iterator(nums);
        if(nums.size()!=0)
            _next = nums[0];
        if(iter->hasNext())
            iter->next();
	    
	}
	
    // Returns the next element in the iteration without advancing the iterator.
	int peek() {
        
        return _next;
        
	}
	
	// hasNext() and next() should behave the same as in the Iterator interface.
	// Override them if needed.
	int next() {
        
        if(iter->hasNext())
             _next = iter->next();
	    return 	Iterator::next();
	}
	
	bool hasNext() const {
	    
        return Iterator::hasNext();
	}
};