46 lines
1.5 KiB
Python
46 lines
1.5 KiB
Python
import math
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class Solution(object):
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def evalRPN(self, tokens):
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"""
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:type tokens: List[str]
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:rtype: int
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"""
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# operators = {
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# '+': lambda x, y: x + y,
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# '-': lambda x, y: x - y,
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# '*': lambda x, y: x * y,
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# '/': lambda x, y: x / y,
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# }
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# stack = [] # Space: O(n)
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# for token in tokens: # Time: O(n)
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# if token not in operators:
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# stack.append(int(token))
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# else:
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# x = stack.pop(-2)
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# y = stack.pop()
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# stack.append(math.ceil(operators[token](x, y)))
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# return int(stack[-1])
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# Recursion Solution
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print(tokens)
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s = tokens[len(tokens) - 1]
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tokens.pop()
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if(s not in '+-/*'): return int(s)
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else:
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a = self.evalRPN(tokens)
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b = self.evalRPN(tokens)
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# print(a)
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# print(b)
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if(s == "+"): return a + b
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elif(s == "*"): return a * b
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elif(s == "-"): return b - a
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else: return int(float(b)/a)
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obj = Solution()
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print(obj.evalRPN(["2","1","+","3","*"])) # 9
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print(obj.evalRPN(["4","13","5","/","+"])) # 6
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# print(obj.evalRPN(["10","6","9","3","+","-11","*","/","*","17","+","5","+"])) # 22
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# print(obj.evalRPN(["0","3","/"])) # 0
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# print(obj.evalRPN(["3","11","+","5","-"])) # 9
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# print(obj.evalRPN(["3","-4","+"])) # -1
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# print(obj.evalRPN(["3","11","5","+","-"])) # -13 |