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| # 许多特殊情况都没考虑 | |
| # 除数为0 优先级 用户输入字母 括号 | |
| class Stack | |
| def initialize(size) | |
| @stack = Array.new(size) | |
| @sp = 0 | |
| end | |
| def push(value) | |
| @stack[@sp] = value | |
| @sp += 1 | |
| end | |
| def pop | |
| return nil if @sp == 0 | |
| @sp -= 1 | |
| @stack[@sp] | |
| end | |
| def size | |
| @sp | |
| end | |
| def to_string | |
| "#{@sp} elements: #{@stack[0...@sp]}" | |
| end | |
| end | |
| class Calculator | |
| def initialize(input) | |
| @stack = Stack.new(input.length) | |
| input.split().each do |chr| | |
| case chr | |
| when '+', '-', '*', '/' | |
| operate(chr) | |
| else | |
| @stack.push chr.to_i | |
| end | |
| end | |
| end | |
| def operate(operator) | |
| return nil if @stack.size <= 1 | |
| so = @stack.pop | |
| fo = @stack.pop | |
| case operator | |
| when '+' | |
| result = fo + so | |
| when '-' | |
| result = fo - so | |
| when '*' | |
| result = fo * so | |
| when '/' | |
| result = fo / so | |
| end | |
| @stack.push result | |
| end | |
| def to_string | |
| @stack.to_string | |
| end | |
| end | |
| puts 'Give me a string' | |
| input = gets | |
| cal = Calculator.new(input) | |
| p cal.to_string |
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