这是我的堆栈实现。
这种方法的问题在于迭代。迭代是具有破坏性的,因此在迭代结束时调用peek会引发错误。
class Stack:
def __init__(self):
self.head = None
self.size = 0
def push(self, item):
node = Node(item)
if not self.head:
self.head = node
else:
node.next = self.head
self.head = node
self.size += 1
def pop(self):
if self.size == 0:
raise ValueError('Popping off an empty stack!')
item = self.head.val
self.head = self.head.next
return item
def peek(self):
if self.size == 0:
raise ValueError('Peeking into an empty stack!')
return self.head.val
def __iter__(self):
return self
def __next__(self):
if self.head:
curr = self.head
else:
raise StopIteration()
self.head = self.head.next
return curr.val
class Node:
def __init__(self, val):
self.val = val
self.next = None
if __name__ == '__main__':
stack = Stack()
stack.push(12)
stack.push(13)
stack.push(9)
for item in stack:
print(item)
print(stack.peek())
这种方法的问题在于迭代。迭代是具有破坏性的,因此在迭代结束时调用peek会引发错误。
return self.head.val
AttributeError: 'NoneType'对象没有属性'val'
如何使迭代不具有破坏性?