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| 1 | +#================================================== |
| 2 | +#==> Title: |
| 3 | +#==> Author: Zhang zhen |
| 4 | +#==> Email: hustmatnoble.gmail.com |
| 5 | +#==> GitHub: https://github.com/MatNoble |
| 6 | +#==> Date: |
| 7 | +#================================================== |
| 8 | + |
| 9 | +from typing import List |
| 10 | +class Solution: |
| 11 | + def evalRPN(self, tokens: List[str]) -> int: |
| 12 | + n = len(tokens) |
| 13 | + # if n < 3: return False |
| 14 | + i = res = 0 |
| 15 | + stack = [] |
| 16 | + while i<n: |
| 17 | + if tokens[i] == '+': |
| 18 | + tmp = stack.pop() |
| 19 | + res = stack.pop() + tmp |
| 20 | + elif tokens[i] == '-': |
| 21 | + tmp = stack.pop() |
| 22 | + res = stack.pop() - tmp |
| 23 | + elif tokens[i] == '*': |
| 24 | + tmp = stack.pop() |
| 25 | + res = stack.pop() * tmp |
| 26 | + elif tokens[i] == '/': |
| 27 | + tmp = stack.pop() |
| 28 | + res = int(stack.pop() / tmp) |
| 29 | + else: |
| 30 | + res = int(tokens[i]) |
| 31 | + stack.append(res) |
| 32 | + i += 1 |
| 33 | + return stack[0] |
| 34 | + |
| 35 | +mat = Solution() |
| 36 | +tokens = ["2", "1", "+", "3", "*"] |
| 37 | +# tokens = ["4", "13", "5", "/", "+"] |
| 38 | +# tokens = ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"] |
| 39 | +tokens = ["18"] |
| 40 | +mat.evalRPN(tokens) |
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