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valid_parentheses.py
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valid_parentheses.py
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def isValid(s):
stack = Stack()
brackets = {"]": "[", "}": "{", ")": "("}
for l in s:
if l in brackets.values():
stack.push(l)
elif l in brackets.keys() and stack.length > 0:
found = stack.pop(brackets[l])
if found:
continue
else:
return False
elif l in brackets.keys() and stack.length <= 0:
return False
stack.print()
return stack.length == 0
class Stack ():
def __init__(self):
self.length = 0
self.head = None
def print(self):
if not self.head:
return
list = []
current = self.head
while current:
list.append(current.value)
current = current.prev
stdout = " -> ".join(list)
print(stdout)
def push (self, value):
current = Node(value, None)
self.length += 1
if not self.head:
self.head = current
else:
current.prev = self.head
self.head = current
def pop (self, value):
if self.length > 0:
current = self.head
if current.value == value:
self.head = self.head.prev
current.prev = None
self.length -= 1
return current.value
return False
def peek(self):
if not self.head:
return False
return self.head.value
class Node ():
def __init__(self, value, prev):
self.value = value
self.prev = prev
def main():
s = "[)]"
print(isValid(s))
if __name__ == "__main__":
main()