LeetCode150(2021.3.20)

LC150. 逆波兰表达式求值

class Solution {
    public int evalRPN(String[] tokens) {
        Deque<Integer> stack = new LinkedList<Integer>();
        for (int i = 0; i < tokens.length; ++i) {
            String item = tokens[i];
            if ("+".equals(item)) {
                int num2 = stack.pop();
                int num1 = stack.pop();
                stack.push(num1 + num2);
            }
            else if ("-".equals(item)) {
                int num2 = stack.pop();
                int num1 = stack.pop();
                stack.push(num1 - num2);
            }
            else if ("*".equals(item)) {
                int num2 = stack.pop();
                int num1 = stack.pop();
                stack.push(num1 * num2);
            }
            else if ("/".equals(item)) {
                int num2 = stack.pop();
                int num1 = stack.pop();
                stack.push(num1 / num2);
            }
            else {
                stack.push(Integer.parseInt(item));
            }
        }
        return stack.pop();
    }
}