Time: 25 ms (29.08%), Space: 39 MB (43.14%) - LeetHub

Author: hajin-kim

0150-evaluate-reverse-polish-notation/0150-evaluate-reverse-polish-notation.kt

@@ -0,0 +1,31 @@
+import java.util.Stack
+
+class Solution {
+    private val OPERATORS = arrayOf(
+        "+", "-", "*", "/"
+    )
+
+    fun evalRPN(tokens: Array<String>): Int {
+        val numbers = Stack<Int>()
+
+        for (token in tokens) {
+            if (token !in OPERATORS) {
+                numbers.push(token.toInt())
+            } else {
+                val op2 = numbers.pop()
+                val op1 = numbers.pop()
+
+                val result = when (token) {
+                    "+" -> op1 + op2
+                    "-" -> op1 - op2
+                    "*" -> op1 * op2
+                    else -> op1 / op2
+                }
+
+                numbers.push(result)
+            }
+        }
+
+        return numbers.pop()
+    }
+}