150. 逆波兰表达式求值

150. 逆波兰表达式求值

class Solution {
    public int evalRPN(String[] tokens) {
        Deque<Integer> stack = new LinkedList<>();
        for (String token : tokens) {
            if (token.equals("+")) {
                stack.push(stack.pop() + stack.pop());
            } else if (token.equals("-")) {
                int num1 = stack.pop();
                int num2 = stack.pop();
                stack.push(num2 - num1);
            } else if (token.equals("*")) {
                stack.push(stack.pop() * stack.pop());
            } else if (token.equals("/")) {
                int num1 = stack.pop();
                int num2 = stack.pop();
                stack.push(num2 / num1);
            } else {
                stack.push(Integer.parseInt(token));
            }
        }
        return stack.peek();
    }
}