1. Time complexity (large o notation) and implementation of stacks using Python

1. Time complexity (large o notation):

O (1) < O (logn) < O (n) < O (Nlogn) < O (N2) < O (n3) < O (2n) < O (n!) < O (NN)

　　　

(1) Time complexity of commonly used data structures in Python:

The time complexity of the list built-in operations:

　　　　　　　　

Dict time complexity for built-in operations:

　　　　　　

(2) Abstract datatype (adt:abstract data type):

Common data Operations (5 types):

　　　　　　　Increase (insert)

　　　　　　　deleting (deleting)

　　　　　　　Change (change)

　　　　　　　Check (Find)

　　　　　　　Sort

2. The implementation of the stack:

(1) The performance of the stack:

　　　　　

(2) The operation of the stack:

　　　　stack (): Create a new empty stack

　　　　push (item): Add a new element item to the top of the stack

　　　　pop (): Pop-up stack top element

　　　　Peek (): Returns the top element of the stack

　　　　is_empty (): Determines whether the stack is empty

　　　　size (): Returns the number of elements in the stack

(3) Implementation stack:　　　　

1 classStack (object):2     """implementation of the stack"""3     def __init__(self):4Self.__list= []5 6     #Add a new element item to the top of the stack7     defpush (self, item):8Self.__list. Append (item)9 Ten     #pop-up stack top element One     defpop (self): A         returnSelf.__list. Pop () -  -     #returns the top element of the stack the     defPeek (self): -         ifSelf.__list: -             returnSelf.__list[-1] -         Else: +             returnNone -  +     #determine if the stack is empty A     defIs_empty (self): at         returnSelf.__list== [] -  -     #returns the number of elements in the stack -     defsize (self): -         returnLen (self.__list) -  in  - if __name__=="__main__": tos =Stack () +S.push (1) -S.push (2) theS.push (3) *S.push (4) $ Panax Notoginseng     Print(S.pop ()) -     Print(S.pop ()) the     Print(S.pop ()) +     Print(S.pop ())

　　　　　　Operation Result:

　　　　　　

1. Time complexity (large o notation) and implementation of stacks using Python