Package g0101_0200.s0150_evaluate_reverse_polish_notation

Class Solution

java.lang.Object

g0101_0200.s0150_evaluate_reverse_polish_notation.Solution

public class Solution
extends Object

150 - Evaluate Reverse Polish Notation.<p>Medium</p> <p>Evaluate the value of an arithmetic expression in <a href="http://en.wikipedia.org/wiki/Reverse_Polish_notation" target="_top">Reverse Polish Notation</a>.</p> <p>Valid operators are <code>+</code>, <code>-</code>, <code>*</code>, and <code>/</code>. Each operand may be an integer or another expression.</p> <p><strong>Note</strong> that division between two integers should truncate toward zero.</p> <p>It is guaranteed that the given RPN expression is always valid. That means the expression would always evaluate to a result, and there will not be any division by zero operation.</p> <p><strong>Example 1:</strong></p> <p><strong>Input:</strong> tokens = [&ldquo;2&rdquo;,&ldquo;1&rdquo;,&ldquo;+&rdquo;,&ldquo;3&rdquo;,&ldquo;*&rdquo;]</p> <p><strong>Output:</strong> 9</p> <p><strong>Explanation:</strong> ((2 + 1) * 3) = 9</p> <p><strong>Example 2:</strong></p> <p><strong>Input:</strong> tokens = [&ldquo;4&rdquo;,&ldquo;13&rdquo;,&ldquo;5&rdquo;,&ldquo;/&rdquo;,&ldquo;+&rdquo;]</p> <p><strong>Output:</strong> 6</p> <p><strong>Explanation:</strong> (4 + (13 / 5)) = 6</p> <p><strong>Example 3:</strong></p> <p><strong>Input:</strong> tokens = [&ldquo;10&rdquo;,&ldquo;6&rdquo;,&ldquo;9&rdquo;,&ldquo;3&rdquo;,&ldquo;+&rdquo;,&ldquo;-11&rdquo;,&ldquo;*&rdquo;,&ldquo;/&rdquo;,&ldquo;*&rdquo;,&ldquo;17&rdquo;,&ldquo;+&rdquo;,&ldquo;5&rdquo;,&ldquo;+&rdquo;]</p> <p><strong>Output:</strong> 22</p> <p><strong>Explanation:</strong></p> <pre><code> ((10 \* (6 / ((9 + 3) \* -11))) + 17) + 5 = ((10 \* (6 / (12 \* -11))) + 17) + 5 = ((10 \* (6 / -132)) + 17) + 5 = ((10 \* 0) + 17) + 5 = (0 + 17) + 5 = 17 + 5 = 22 </code></pre> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= tokens.length <= 10⁴</code></li> <li><code>tokens[i]</code> is either an operator: <code>&quot;+&quot;</code>, <code>&quot;-&quot;</code>, <code>&quot;*&quot;</code>, or <code>&quot;/&quot;</code>, or an integer in the range <code>[-200, 200]</code>.</li> </ul>

Constructor Summary

Constructors

Constructor	Description
Solution()

Method Summary

Modifier and Type	Method	Description
int	evalRPN(String[] tokens)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Solution

public Solution()

Method Details

evalRPN

public int evalRPN(String[] tokens)