150. 逆波兰表达式求值（算法200题-77）

var evalRPN = function (tokens) {
    const stack = []
    let temp = ''
    for (let i = 0; i < tokens.length; i++) {
        temp = tokens[i]
        switch (temp) {
            case '+':
                stack.push(stack.pop() + stack.pop())
                break
            case '-':
                temp = stack.pop()
                stack.push(stack.pop() - temp)
                break
            case '*':
                stack.push(stack.pop() * stack.pop())
                break
            case '/':
                temp = stack.pop()
                stack.push(Math.trunc(stack.pop() / temp))
                break
            default:
                stack.push(Number(temp))
                break
        }
    }
    return stack.pop()
};