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Solved using recursion

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This commit is contained in:
Jacob Delgado 2023-09-27 07:41:44 -07:00
parent b285140f84
commit 9f70612630
1 changed files with 33 additions and 45 deletions
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76
NeetCodeRoadmap/Stack/150_Evaluate_Reverse_Polish_Notation.py
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@ -5,52 +5,40 @@ class Solution(object):
:type tokens: List[str]
:rtype: int
"""
valid_tokens = {
'+': lambda x, y: x + y,
'-': lambda x, y: x - y,
'*': lambda x, y: x * y,
'/': lambda x, y: x / y,
}
tmp = []
# operators = {
# '+': lambda x, y: x + y,
# '-': lambda x, y: x - y,
# '*': lambda x, y: x * y,
# '/': lambda x, y: x / y,
# }
# stack = [] # Space: O(n)
# for token in tokens: # Time: O(n)
# if token not in operators:
# stack.append(int(token))
# else:
# x = stack.pop(-2)
# y = stack.pop()
# stack.append(math.ceil(operators[token](x, y)))
# return int(stack[-1])
# while len(tokens) != 1:
blanks = 0
count = 0
for x in range(len(tokens)):
# print(tokens[x])
if tokens[x] in valid_tokens:
operator = valid_tokens[tokens[x]]
if len(tmp) > 1 and count == 0:
a = tmp.pop()
b = tmp.pop()
tokens.append(math.floor(operator(b, a)))
# print(tmp)
# print(tokens)
tokens[x] = None
count += 1
else:
a = tmp.pop()
b = tokens.pop()
tokens.append(math.ceil(operator(a, b)))
tokens[x] = None
else:
tmp.append(int(tokens[x]))
tokens[x] = None
# print(tokens)
# print(tmp)
for y in tokens:
if y is None:
blanks += 1
# print(blanks)
tokens = tokens[blanks:]
if tokens[0] < 0:
tokens[0] *= -1
return int(tokens[0])
# Recursion Solution
s = tokens[len(tokens) - 1]
tokens.pop()
print(tokens)
if(s not in '+-/*'): return int(s)
else:
a = self.evalRPN(tokens)
b = self.evalRPN(tokens)
if(s == "+"): return a + b
elif(s == "*"): return a * b
elif(s == "-"): return b - a
else: return int(float(b)/a)
obj = Solution()
# print(obj.evalRPN(["2","1","+","3","*"])) # 9
# print(obj.evalRPN(["4","13","5","/","+"])) # 6
# print(obj.evalRPN(["10","6","9","3","+","-11","*","/","*","17","+","5","+"])) # 22
# print(obj.evalRPN(["0","3","/"])) # 0
print(obj.evalRPN(["2","1","+","3","*"])) # 9
print(obj.evalRPN(["4","13","5","/","+"])) # 6
print(obj.evalRPN(["10","6","9","3","+","-11","*","/","*","17","+","5","+"])) # 22
print(obj.evalRPN(["0","3","/"])) # 0
print(obj.evalRPN(["3","11","+","5","-"])) # 9
print(obj.evalRPN(["3","-4","+"])) # -1
print(obj.evalRPN(["3","11","5","+","-"])) # -13