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package problems;

import java.util.ArrayDeque;

import java.util.Deque;

import java.util.LinkedList;

public class LeetCode150 {

public int evalRPN(String[] tokens) {

Deque<Integer> stack = new LinkedList<Integer>();

int n = tokens.length;

for (int i = 0; i < n; i++) {

String token = tokens[i];

if (isNumber(token)) {

stack.push(Integer.parseInt(token));

} else {

int num2 = stack.pop();

int num1 = stack.pop();

switch (token) {

case "+":

stack.push(num1 + num2);

break;

case "-":

stack.push(num1 - num2);

break;

case "*":

stack.push(num1 * num2);

break;

case "/":

stack.push(num1 / num2);

break;

default:

}

}

}

return stack.pop();

}

public boolean isNumber(String token) {

return !("+".equals(token) || "-".equals(token) || "*".equals(token) || "/".equals(token));

}

}