题目：

题解：

type PeekingIterator struct {iter     *Iterator_hasNext bool_next    int
}func Constructor(iter *Iterator) *PeekingIterator {return &PeekingIterator{iter, iter.hasNext(), iter.next()}
}func (it *PeekingIterator) hasNext() bool {return it._hasNext
}func (it *PeekingIterator) next() int {ret := it._nextit._hasNext = it.iter.hasNext()if it._hasNext {it._next = it.iter.next()}return ret
}func (it *PeekingIterator) peek() int {return it._next
}