Python data structures and algorithms--stacks

# stack
# In fact, the list in Python can be used as a stack, with Collections.deque can also
# 1. Into the stack list.append (item)
# 2. Out Stack item = List.pop ()
# 3. For the first element out of the stack, you can also item = List.pop (0) and the queue concept
# 4. In fact, you can also take any element out of the Stack item = List.pop (i) is equivalent to deleting element i
# Note that 3,4 is time-consuming.

Stacks can be conveniently used to determine whether a string is a palindrome, but to find the largest palindrome in a long string is the suffix tree.

The following is a stack-based palindrome judgment algorithm

1 #determine if a string is a palindrome (Plalindrome is not Moslems =_=| |)2 #If a string is a palindrome, it must be in the middle symmetry3 #put the first half into the stack, and then the stack to see if you can match the character one by one after mid4 5 defIs_plalindrome_demo1 (A):6MID = Len (A)/2#5/2=2, 4/2=27stack = []8      forIinchRange (mid):9 stack.append (A[i])Ten      One     ifLen (A)%2 = = 0:#determine whether the length of a string is odd or even ANext = mid#determine the starting subscript for the post-half string -     Else: -Next = mid + 1 the  -top = Mid-1 -      forIinchRange (Next,len (A)): -         ifStack[top]! =A[i]: +             returnFalse -Top-= 1 +      A     returnTrue

Test:

if __name__= ="__main__"    := List ("Hahahahahahahahaha  ")    print is_plalindrome_demo1 (q)

Manual implementation Stack

1 #simple filo stack category2 classStack:3     def __init__(self):4Self.top = None#point to top of stack5Self.end = None#Point to the bottom of the stack6Self.count =07         8     defpush (Self,data):9         ifSelf.end = =None:TenSelf.end =Node (data) OneSelf.top =Self.end A         Else: -temp = Self.top#Save current stack top -Self.top =Node (data) theSelf.top.next =Temp -Self.count + = 1 -      -     defpop (self): +         ifSelf.top = =None: -             Raise "Error:top==none" +data =Self.top.data ASelf.top =Self.top.next atSelf.count-= 1 -         returnData

Python data structures and algorithms--stacks