我正在使用Python实现在链表的头部插入。我在引用这个guide。对于案例2,我发现我必须添加return self.head
以使驱动程序代码正确插入头部,否则它将不会终止。为什么呢?我认为第一行足够了,因为我调用这个方法来修改链表。我为什么要回来
以下是节点前插入的代码:
class LinkedList:
# note nodes = Node set the default (no argument) initialization
def __init__(self, nodes = None):
self.head = None
if nodes is not None:
# .pop(index) method remove the element from an array-like container and return it
node = Node(nodes.pop(0))
self.head = node
# loop through the rest elements in nodes (2nd now became the 1st in nodes)
for elem in nodes:
node.next = Node(elem)
node = node.next
def insert_before(self, targetn_data, newn):
# case1: empty list
if self.head is None:
raise Exception('empty llist')
# case2: insert before head (newn becomes new head)
if targetn_data == self.head.data:
print(f'inserting {newn} at the head')
newn.next = self.head
self.head = newn
################# Why? ##################
return self.head
#########################################
# case3: in between. use runner technique
...
驱动程序代码:
def main():
nodes = [1, 2, 3, 4, 5, 6]
# instantiate a linked list using __init__ method we defined
llist = LinkedList(nodes)
# insert_before driver code
llist.insert_before(1, Node(100))
llist.insert_before(6, Node(90))
print(f'prints out the llist after insert_before: \n {llist}\n')
让我举例说明
对于单个if-else代码看起来很幼稚,但对于大型嵌套if-else代码来说会有很大帮助
但是,如果可以的话,这是一个很好的编码原则
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