Evaluate Reverse Polish Notation

Problem

Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are +, -, *, /. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6

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Idea

用stack来解，维护这个栈存储所有的number，如果碰到了操作符"+","-","*","/"则弹出两个栈里的数分别做右操作数和左操作数，然后把计算结果再压栈

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Note

Convert string to int

Convert int to string

You cann't do switch-case statement on string by C++

Solution

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