鏈表

單鏈

class Node:
    def __init__(self,item=None):
        self.item=item
        self.next=None
class SingleLink:
    def __init__(self):
        self.head=None
    def is_empty(self):
        return self.head==None
    def length(self):
        current=self.head
        count=0
        if current !=None:
            count+=1
            current=current.next
        return count
    def add(self,item):
        node = Node(item)
        node.next=self.head
        self.head=node
    def append(self,item):
        node=Node(item)
        if self.is_empty():
            self.head = node
        else:
            #將指針指向最後一個元素
            current=self.head
            while current.next!=None:
                current=current.next
            current.next=node
    def insert(self,pos,item):
        if pos<=0:
            self.add(item)
        elif pos>self.length()-1:
            self.append(item)
        else:
            node = Node(item)
            per = self.head
            count=0
            while count<pos-1:
                count+=1
                per=per.next
            node.next=per.next
            per.next=node

    def remove(self,item):
        current=self.head
        per=None
        while current != None:
            if current.item==item:
                if current == self.head:
                    self.head=current.next
                else:
                    per.next=current.next
                break
            else:
                per = current
                current=current.next

    def seach(self,item):
        current = self.head
        flag=False
        while not flag and current !=None:
            if current.item==item:
                flag=True
            else:
                current = current.next
        return flag

    def index(self,item):
        current = self.head
        index=0
        while current !=None:
            if current.item==item:
                return index
            else:
                index+=1
                current=current.next
        return -1

if __name__=="__main__":
    sl=SingleLink()
    sl.append(1)
    print(sl.is_empty())
    print(sl.seach(1))
    sl.append(2)
    print(sl.index(3))

循環單鏈