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min_stack.py
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min_stack.py
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# MinStack and BetterMinStack:
import math
class MinStack():
def __init__(self):
self.s = []
def push(self, n):
if len(self.s) == 0:
self.s.append({'value': n, 'min': n})
else:
prev = self.s[-1]
self.s.append({'value': n, 'min': min(prev['min'], n)})
def pop(self):
return self.s.pop()['value']
def min(self):
if len(self.s) == 0:
return math.inf
return self.s[-1]['min']
s = MinStack()
s.push(3)
s.push(2)
s.push(4)
s.push(1)
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min())
class BetterMinStack():
def __init__(self):
self.s = []
self.min_stack = []
def push(self, n):
length = len(self.min_stack)
if length == 0 or n < self.min_stack[length-1]:
self.min_stack.append(n)
self.s.append(n)
def pop(self):
output = self.s.pop()
if output == self.min_stack[-1]:
self.min_stack.pop()
return output
def min(self):
if len(self.min_stack) == 0:
return math.inf
return self.min_stack[-1]
s = BetterMinStack()
s.push(3)
s.push(2)
s.push(4)
s.push(1)
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min(), s.pop())
print(s.min())