python 链表——单向链表的增、删、改、查

单向链表



单向链表的节点实现

class SingleNode(object):
    """单链表的节点"""
    def __init__(self, item):
        self.item = item
        self.next = None

 

 

单链表的操作

​​​​is_empty() #链表是否为空
length()  # 链表长度
travel()  # 遍历整个链表
add()     #链表头部添加元素
append()   #链表尾部添加元素
insert()   #链表中间插入元素
remove()   #删除节点
search()   #查找节点是否存在
 

 

class linkList(object):
    """单链表"""
    def __init__(self):
        self.head = None

    def is_empty(self):
        """判断链表是否为空"""
        return self.head == None

    def length(self):
        """链表长度"""
        cur = self.head
        count = 0
        while cur != None:
            count += 1
            cur = cur.next
        return count

    def travel(self):
        """遍历链表"""
        cur = self.head
        while cur != None:
            print(cur.item)
            cur = cur.next

    def add(self, item):
        """头部添加链表元素"""
        node = SingleNode(item)
        node.next = self.head
        self.head = node

    def append(self, item):
        """尾部添加元素"""
        node = SingleNode(item)
        if self.is_empty():
            self.head = node
        else:
            cur = self.head
            while cur.next != None:
                cur = cur.next
            cur.next = node

    def insert(self, pos, item):
        """指定位置添加元素"""
        if pos <= 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append(item)
        else:
            node = SingleNode(item)
            count = 0
            pre = self.head
            while count < (pos-1):
                count += 1
                pre = pre.next
            node.next = pre.next
            pre.next = node

    def remove(self, item):
        """删除节点"""
        cur = self.head
        pre = None
        while cur != None:
            if cur.item == item:
                """如果删除的是第一个节点"""
                if not pre:
                    self.head = cur.next
                else:
                    pre.next = cur.next
                break
            else:
                """后移节点"""
                pre = cur
                cur = cur.next

    def search(self, item):
        """判断节点是否存在"""
        cur = self.head
        while cur != None:
            if cur.item == item:
                return True
            cur = cur.next
        return False

"""测试"""
if __name__ == "__main__":
    ll = linkList()
    ll.add(1)
    ll.add(2)
    ll.append(3)
    ll.insert(2,4)
    print("length:",ll.length())
    ll.travel()
    print(ll.search(3))
    print(ll.search(5))
    ll.remove(1)
    print("length:",ll.length())
    ll.travel()

运行结果为：

length: 4
2
1
4
3
True
False
length: 3
2
4
3