best python stack implementation
class Stack:
def __init__(self):
self.items = []
def isEmpty(self):
return self.items == []
def push(self, item):
self.items.append(item)
def pop(self):
return self.items.pop()
def peek(self):
return self.items[len(self.items)-1]
def size(self):
return len(self.items)stack data structure python
#using doubly linked list
from collections import deque
myStack = deque()
myStack.append('a')
myStack.append('b')
myStack.append('c')
myStack
deque(['a', 'b', 'c'])
myStack.pop()
'c'
myStack.pop()
'b'
myStack.pop()
'a'
myStack.pop()
#Traceback (most recent call last):
#File "<console>", line 1, in <module>
##IndexError: pop from an empty dequedef dft(self, array): stack = Stack() visited = set() stack.append(self) while len(stack) > 0 and while len(visited) >= 0: current = stack.pop() array.append(current) visited.add(current) return array
def dft(self, array):
stack = Stack()
visited = set()
stack.append(self)
while len(stack) > 0 and while len(visited) >= 0:
current = stack.pop()
array.append(current)
visited.add(current)
return arraystack in python
stack = []
# add element in the stack.
stack.append('a')
# delete in LIFO order.
stack.pop()python dijkstra implementation stack
nodes = ('A', 'B', 'C', 'D', 'E', 'F', 'G')
distances = {
'B': {'A': 5, 'D': 1, 'G': 2},
'A': {'B': 5, 'D': 3, 'E': 12, 'F' :5},
'D': {'B': 1, 'G': 1, 'E': 1, 'A': 3},
'G': {'B': 2, 'D': 1, 'C': 2},
'C': {'G': 2, 'E': 1, 'F': 16},
'E': {'A': 12, 'D': 1, 'C': 1, 'F': 2},
'F': {'A': 5, 'E': 2, 'C': 16}}
unvisited = {node: None for node in nodes} #using None as +inf
visited = {}
current = 'B'
currentDistance = 0
unvisited[current] = currentDistance
while True:
for neighbour, distance in distances[current].items():
if neighbour not in unvisited: continue
newDistance = currentDistance + distance
if unvisited[neighbour] is None or unvisited[neighbour] > newDistance:
unvisited[neighbour] = newDistance
visited[current] = currentDistance
del unvisited[current]
if not unvisited: break
candidates = [node for node in unvisited.items() if node[1]]
current, currentDistance = sorted(candidates, key = lambda x: x[1])[0]
print(visited)Copyright © 2021 Codeinu
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