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- symbol_priority = {}
- symbol_priority[0] = ['#']
- symbol_priority[1] = ['(']
- symbol_priority[2] = ['+', '-']
- symbol_priority[3] = ['*', '/']
- symbol_priority[4] = [')']
- def comparePriority(symbol, RPN_stack, symbol_stack):
- global symbol_priority
- if len(symbol_stack) > 0:
- symbol_pop = symbol_stack.pop()
- else:
- return
- for list in symbol_priority.values():
- if (symbol in list) and (symbol_pop in list):
- symbol_stack.append(symbol_pop)
- symbol_stack.append(symbol)
- return
- elif symbol in list:
- RPN_stack.append(symbol_pop)
- comparePriority(symbol, RPN_stack, symbol_stack)
- return
- elif symbol_pop in list:
- symbol_stack.append(symbol_pop)
- symbol_stack.append(symbol)
- return
- else:
- continue
- symbol_stack.append(symbol_pop)
- return
- def scanEveryone(input_string, RPN_stack, symbol_stack):
- for ch in input_string:
- if ch.isdigit():
- RPN_stack.append(ch)
- else:
- if len(symbol_stack) > 0:
- if ch == '(':
- symbol_stack.append(ch)
- elif ch == ')':
- while True:
- symbol_pop = symbol_stack.pop()
- if symbol_pop == '(':
- break
- else:
- RPN_stack.append(symbol_pop)
- else:
- comparePriority(ch, RPN_stack, symbol_stack)
- else:
- symbol_stack.append(ch)
- def scanInput(RPN_stack, symbol_stack):
- input_string = raw_input()
- input_string += '#'
- scanEveryone(input_string, RPN_stack, symbol_stack)
- def calRPN(RPN_stack):
- value_stack = []
- RPN_stack.append('#')
- for value in RPN_stack:
- if value == '#':
- return value_stack.pop()
- break
- if value.isdigit():
- value_stack.append(value)
- else:
- right_value = value_stack.pop()
- left_value = value_stack.pop()
- cal_string = left_value + value + right_value
- value_stack.append(str(eval(cal_string)))
- def main():
- RPN_stack = []
- symbol_stack = []
- scanInput(RPN_stack, symbol_stack)
- print calRPN(RPN_stack)
- if __name__ == '__main__':
- main()
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