Create StackApplications.java

Author: aayush-raj2

Linear_Data_Structures/01_Stack/StackApplications.java

@@ -0,0 +1,47 @@
+// Author: Aayush Raj
+// Description: Demonstrates Undo simulation and postfix evaluation using Stack
+
+import java.util.Stack;
+
+public class StackApplications {
+    public static int evaluatePostfix(String expr) {
+        Stack<Integer> stack = new Stack<>();
+
+        for (char c : expr.toCharArray()) {
+            if (Character.isDigit(c))
+                stack.push(c - '0');
+            else {
+                int val2 = stack.pop();
+                int val1 = stack.pop();
+                switch (c) {
+                    case '+': stack.push(val1 + val2); break;
+                    case '-': stack.push(val1 - val2); break;
+                    case '*': stack.push(val1 * val2); break;
+                    case '/': stack.push(val1 / val2); break;
+                }
+            }
+        }
+        return stack.pop();
+    }
+
+    public static void main(String[] args) {
+        System.out.println("Undo Simulation using Stack:");
+        Stack<String> actions = new Stack<>();
+        actions.push("Typed 'Hello'");
+        actions.push("Typed 'World'");
+        System.out.println(actions.pop() + " undone!");
+
+        System.out.println("\nPostfix Evaluation:");
+        String postfix = "53*2+";
+        System.out.println("Result: " + evaluatePostfix(postfix));
+    }
+}
+
+/*
+🖥️ Output:
+Undo Simulation using Stack:
+Typed 'World' undone!
+
+Postfix Evaluation:
+Result: 17
+*/