feat: Add MinStackUsingTwoStacks new algorithm with Junit tests (#5758)

src/main/java/com/thealgorithms/stacks/MinStackUsingTwoStacks.java

@@ -0,0 +1,57 @@
+package com.thealgorithms.stacks;
+
+import java.util.Stack;
+
+/**
+ * Min-Stack implementation that supports push, pop, and retrieving the minimum element in constant time.
+ *
+ * @author Hardvan
+ */
+public final class MinStackUsingTwoStacks {
+    MinStackUsingTwoStacks() {
+    }
+
+    private final Stack<Integer> stack = new Stack<>();
+    private final Stack<Integer> minStack = new Stack<>();
+
+    /**
+     * Pushes a new element onto the {@code stack}.
+     * If the value is less than or equal to the current minimum, it is also pushed onto the {@code minStack}.
+     *
+     * @param value The value to be pushed.
+     */
+    public void push(int value) {
+        stack.push(value);
+        if (minStack.isEmpty() || value <= minStack.peek()) {
+            minStack.push(value);
+        }
+    }
+
+    /**
+     * Removes the top element from the stack.
+     * If the element is the minimum element, it is also removed from the {@code minStack}.
+     */
+    public void pop() {
+        if (stack.pop().equals(minStack.peek())) {
+            minStack.pop();
+        }
+    }
+
+    /**
+     * Retrieves the top element of the stack.
+     *
+     * @return The top element.
+     */
+    public int top() {
+        return stack.peek();
+    }
+
+    /**
+     * Retrieves the minimum element in the stack.
+     *
+     * @return The minimum element.
+     */
+    public int getMin() {
+        return minStack.peek();
+    }
+}