Peeking_iterator.cpp

class PeekingIterator : public Iterator {
    int next_val; // keep a variable for storing the "next value" for use in "peek" function
    bool iter_hasnext; // for storing the "has next value"
public:
	PeekingIterator(const vector<int>& nums) : Iterator(nums) {
        iter_hasnext=Iterator::hasNext(); // store current has_next value
	    if (iter_hasnext)
            next_val = Iterator::next(); // store the "next_val" for "future" use in "peek" function
	}
	
	int peek() {
        return next_val; // return current next_val
	}
	
	int next() {
	    int curr_next = next_val; // store the current next for returning
        
        iter_hasnext=Iterator::hasNext(); // change the iter_hasnext variable
	    if (iter_hasnext) 
            next_val = Iterator::next(); // change the next_val and move the iterator to next position
        
	    return curr_next; // return the previously stored current next
	}
	
	bool hasNext() const {
	    return iter_hasnext; // return current iter_hashnext value
	}
};