feat: 후위 표기법으로 작성된 수식을 계산하는 기능 예제코드 구현

Author: ksundong

yoonexample/src/main/java/stack/PostCalculator.java

@@ -0,0 +1,34 @@
+package stack;
+
+public class PostCalculator {
+
+  public int calculate(char[] input) {
+    Stack<Integer> stack = new ListStack<>();
+
+    for (char tok : input) {
+      if (Character.isDigit(tok)) {
+        stack.push(Character.getNumericValue(tok));
+      } else {
+        int op2 = stack.pop();
+        int op1 = stack.pop();
+
+        switch (tok) {
+          case '+':
+            stack.push(op1 + op2);
+            break;
+          case '-':
+            stack.push(op1 - op2);
+            break;
+          case '*':
+            stack.push(op1 * op2);
+            break;
+          case '/':
+            stack.push(op1 / op2);
+            break;
+        }
+      }
+    }
+
+    return stack.pop();
+  }
+}

yoonexample/src/test/java/stack/PostCalculatorTest.java

@@ -1,5 +1,7 @@
 package stack;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;