python实现之极简stack和quene

class Node:
    def __init__( self, val ):
        self.val = val
        self.next = None

class Stack:
    def __init__( self ):
        self.top = None

    def peek( self ):
        return self.top 

    def pop( self ):
        if not self.top:
            return None
        else:
            old_top = Node( self.top.val )
            self.top = self.top.next
            return old_top

    def push( self, val ):
        node = Node( val )
        node.next = self.top
        self.top = node

class Quene:
    def __init__( self ):
        self.first = None
        self.last = None

    def dequene( self ):
        if not self.first:
            return None
        else:
            node = Node( self.first.val )
            self.first = self.first.next
            return node

    def enquene( self, val ):
        if not self.last:
            node = Node( val )
            self.first = node
            self.last = node
        else:
            node = Node( val )
            self.last.next = node
            self.last = node

‘‘‘
test case
‘‘‘
s = Stack()
s.push( 1 )
s.push( 0 )
s.push( -1 )
s.push( -1 )
s.push( 6 )
print( s.peek().val )

s.pop()
print( s.peek().val )

s.pop()
s.pop()
s.pop()
print( s.peek().val )

s.pop()
print( s.top )

‘‘‘
Quene test case
‘‘‘
q = Quene()
q.enquene( 1 )
q.enquene( 2 )
q.enquene( 0 )
q.enquene( -1 )
q.enquene( 8 )
q.dequene()
print( q.first.val )