Solution.go

/*   Below is the interface for Iterator, which is already defined for you.
 *
 *   type Iterator struct {
 *
 *   }
 *
 *   func (this *Iterator) hasNext() bool {
 *		// Returns true if the iteration has more elements.
 *   }
 *
 *   func (this *Iterator) next() int {
 *		// Returns the next element in the iteration.
 *   }
 */

type PeekingIterator struct {
	iter          *Iterator
	hasPeeked     bool
	peekedElement int
}

func Constructor(iter *Iterator) *PeekingIterator {
	return &PeekingIterator{iter, iter.hasNext(), iter.next()}
}

func (this *PeekingIterator) hasNext() bool {
	return this.hasPeeked || this.iter.hasNext()
}

func (this *PeekingIterator) next() int {
	if !this.hasPeeked {
		return this.iter.next()
	}
	this.hasPeeked = false
	return this.peekedElement
}

func (this *PeekingIterator) peek() int {
	if !this.hasPeeked {
		this.peekedElement = this.iter.next()
		this.hasPeeked = true
	}
	return this.peekedElement
}