A stack is a data structure that follows the LIFO (Last In, First Out) principle. In other words, The last element we add to a stack is the first one to be removed. When we add (or push) elements to a stack, they are placed on top; i.e. above all the previously-added elements.
There may be certain scenarios where we need to add an element at the bottom of the stack. There are multiple ways to add an element to the bottom of the stack. they are ?
- Using Auxiliary Stack
- Using Recursion
- Using temporary variable
- Using a Queue
Using Auxiliary Stack
We can insert an element at the bottom of a stack using an auxiliary stack (a secondary stack using which we will perform operations) in Java. Here, we will use two stacks (a main stack and an auxiliary stack) to insert an element at the bottom of the main stack.
The main stack will have the original elements, while the auxiliary stack will help us to rearrange the elements. This method is easy to understand.
Steps
Following are the steps to insert an element at the bottom of a stack using an auxiliary stack:
- Initialize Two Stacks: Create a main stack push some elements in it and then create an auxiliary stack.
- Pop All Elements:?Then remove all elements from the main stack and push them into the second auxiliary stack. This will help us to reverse the order of elements.
- Push the New Element: Once the main stack is empty, we need to push the new element into the main stack or you can also push the element on top of the auxiliary stack if you want.
- Restore the Original Order: Pop all elements from the auxiliary stack and push them back into the main stack. This will restore the original order of elements.
Example
Following is an example of how we can use an auxiliary stack to add an element at the bottom ?
import java.util.Stack; public class InsertAtBottomUsingTwoStacks { public static void insertElementAtBottom(Stack<Integer> mainStack, int x) { // Create an extra auxiliary stack Stack<Integer> St2 = new Stack<>(); /* Step 1: Pop all elements from the main stack and push them into the auxiliary stack */ while (!mainStack.isEmpty()) { St2.push(mainStack.pop()); } // Step 2: Push the new element into the main stack mainStack.push(x); /* Step 3: Restore the original order by popping each element from the auxiliary stack and push back to main stack */ while (!St2.isEmpty()) { mainStack.push(St2.pop()); } } public static void main(String[] args) { Stack<Integer> stack1 = new Stack<>(); stack1.push(1); stack1.push(2); stack1.push(3); stack1.push(4); System.out.println("Original Stack: " + stack1); insertElementAtBottom(stack1, 0); System.out.println("Stack after inserting 0 at the bottom: " + stack1); } }
In the program above, we start by pushing the elements 1, 2, 3, and 4 into the stack. Then, we transfer these elements to another stack. After that, we insert the target element into the main stack. Finally, we retrieve all the elements back from the auxiliary stack.
Using Recursion
Recursion is one other way to insert an element at the bottom of a stack. In this approach, we will use a recursive function to pop all the elements from our stack until it becomes empty, and once it becomes empty we will insert the new element into the stack, and then push the elements back into the stack.
Steps
Here are the steps to insert an element at the bottom of a stack using recursion:
- Base Case: Check if the stack is empty. If it is empty, we will push the new element into the stack.
- Recursive Case: If the stack is not empty, we will pop the top element and call the function recursively.
- Restore Elements: After we are done with inserting the new element, we need to push the previously popped elements back into the stack.
Example
import java.util.Stack; public class InsertAtBottomUsingTwoStacks { public static void insertElementAtBottom(Stack<Integer> mainStack, int x) { // Create an extra auxiliary stack Stack<Integer> St2 = new Stack<>(); /* Step 1: Pop all elements from the main stack and push them into the auxiliary stack */ while (!mainStack.isEmpty()) { St2.push(mainStack.pop()); } // Step 2: Push the new element into the main stack mainStack.push(x); /* Step 3: Restore the original order by popping each element from the auxiliary stack and push back to main stack */ while (!St2.isEmpty()) { mainStack.push(St2.pop()); } } public static void main(String[] args) { Stack<Integer> stack1 = new Stack<>(); stack1.push(1); stack1.push(2); stack1.push(3); stack1.push(4); System.out.println("Original Stack: " + stack1); insertElementAtBottom(stack1, 0); System.out.println("Stack after inserting 0 at the bottom: " + stack1); } }
In the above program, we defined a recursive function that inserts a new element at the bottom of the stack, we then continued to pop the elements from the stack until the stack became empty, then we inserted the new element and after that, we restored the previous elements into the stack.
Using Temporary Variable
We can also achieve the given task using a temporary variable. We use this variable to store the elements while we manipulate the stack. This method is easy and we can implement using a simple loop.
Steps
Following are the steps to insert an element at the bottom of a stack using a temporary variable <
- Initialize a Temporary Variable: Create a variable to temporarily hold the elements as you iterate through the stack.
- Transfer Elements: Then use a loop to pop elements from the stack and store those elements in the temporary variable.
- Insert New Element: Once our stack is empty, then we need to push the new element into the stack.
- Restore Elements: After inserting the element, push the elements from the temporary variable back into the stack.
Example
import java.util.Stack; public class InsertAtBottomUsingRecursion { public static void insertAtElementBottom(Stack<Integer> st, int x) { // Base case: If the stack is empty, push the new element if (st.isEmpty()) { st.push(x); return; } // Recursive case: Pop the top element int top = st.pop(); // Call the function recursively insertAtElementBottom(st, x); // Restore the top element into the stack st.push(top); } public static void main(String[] args) { Stack<Integer> st = new Stack<>(); st.push(1); st.push(2); st.push(3); st.push(4); System.out.println("Original Stack: " + st); insertAtElementBottom(st, 0); System.out.println("Stack after inserting 0 at the bottom: " + st); } }
In this program, we used a temporary array to hold the elements while manipulating the stack. We then insert the new element into the stack and restore the original elements into the stack.
Using a Queue
In this approach, we will use a queue to hold the elements temporarily while inserting a new element at the bottom of the stack. This method is the better way to manage the order of elements. Using a Queue we can a new element to a stack without tampering with the existing elements.
Steps
Following are the steps to insert an element at the bottom of a stack using a queue ?
- Initialize a Queue: Create a queue to hold the elements from the stack.
- Transfer Elements: Pop the elements from the stack and enqueue them into the queue.
- Insert New Element: Push the new element into the stack.
- Restore Elements: Dequeue the elements from the queue and push them back into the stack.
Example
import java.util.Stack; public class InsertAtBottomUsingTempVar { public static void insertAtElementBottom(Stack<Integer> st, int x) { // Temporary variable to hold elements int[] temp = new int[st.size()]; int index = 0; // Transfer elements to temporary variable while (!st.isEmpty()) { temp[index++] = st.pop(); } // Push the new element into the stack st.push(x); // Restore elements from temporary variable for (int i = 0; i < index; i++) { st.push(temp[i]); } } public static void main(String[] args) { Stack<Integer> st = new Stack<>(); st.push(1); st.push(2); st.push(3); st.push(4); System.out.println("Original Stack: " + st); insertAtElementBottom(st, 0); System.out.println("Stack after inserting 0 at the bottom: " + st); } }
Output
Following is the output of the above code ?
import java.util.Stack; public class InsertAtBottomUsingTwoStacks { public static void insertElementAtBottom(Stack<Integer> mainStack, int x) { // Create an extra auxiliary stack Stack<Integer> St2 = new Stack<>(); /* Step 1: Pop all elements from the main stack and push them into the auxiliary stack */ while (!mainStack.isEmpty()) { St2.push(mainStack.pop()); } // Step 2: Push the new element into the main stack mainStack.push(x); /* Step 3: Restore the original order by popping each element from the auxiliary stack and push back to main stack */ while (!St2.isEmpty()) { mainStack.push(St2.pop()); } } public static void main(String[] args) { Stack<Integer> stack1 = new Stack<>(); stack1.push(1); stack1.push(2); stack1.push(3); stack1.push(4); System.out.println("Original Stack: " + stack1); insertElementAtBottom(stack1, 0); System.out.println("Stack after inserting 0 at the bottom: " + stack1); } }
In this implementation, we used a queue to hold the elements for a temporary time. We first transfer the existing elements from the stack to the queue. Then, we push the new element into the stack and restore the original elements from the queue back to the stack
Note: We can use other data structures such as Array, LinkedList, ArrayList, etc. instead of a queue.
The above is the detailed content of Java Program to insert an element at the Bottom of a Stack. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Singleton design pattern in Java ensures that a class has only one instance and provides a global access point through private constructors and static methods, which is suitable for controlling access to shared resources. Implementation methods include: 1. Lazy loading, that is, the instance is created only when the first request is requested, which is suitable for situations where resource consumption is high and not necessarily required; 2. Thread-safe processing, ensuring that only one instance is created in a multi-threaded environment through synchronization methods or double check locking, and reducing performance impact; 3. Hungry loading, which directly initializes the instance during class loading, is suitable for lightweight objects or scenarios that can be initialized in advance; 4. Enumeration implementation, using Java enumeration to naturally support serialization, thread safety and prevent reflective attacks, is a recommended concise and reliable method. Different implementation methods can be selected according to specific needs

ThreadLocal is used in Java to create thread-private variables, each thread has an independent copy to avoid concurrency problems. It stores values ??through ThreadLocalMap inside the thread. Pay attention to timely cleaning when using it to prevent memory leakage. Common uses include user session management, database connections, transaction context, and log tracking. Best practices include: 1. Call remove() to clean up after use; 2. Avoid overuse; 3. InheritableThreadLocal is required for child thread inheritance; 4. Do not store large objects. The initial value can be set through initialValue() or withInitial(), and the initialization is delayed until the first get() call.

Optional can clearly express intentions and reduce code noise for null judgments. 1. Optional.ofNullable is a common way to deal with null objects. For example, when taking values ??from maps, orElse can be used to provide default values, so that the logic is clearer and concise; 2. Use chain calls maps to achieve nested values ??to safely avoid NPE, and automatically terminate if any link is null and return the default value; 3. Filter can be used for conditional filtering, and subsequent operations will continue to be performed only if the conditions are met, otherwise it will jump directly to orElse, which is suitable for lightweight business judgment; 4. It is not recommended to overuse Optional, such as basic types or simple logic, which will increase complexity, and some scenarios will directly return to nu.

Analyzing Java heap dumps is a key means to troubleshoot memory problems, especially for identifying memory leaks and performance bottlenecks. 1. Use EclipseMAT or VisualVM to open the .hprof file. MAT provides Histogram and DominatorTree views to display the object distribution from different angles; 2. sort in Histogram by number of instances or space occupied to find classes with abnormally large or large size, such as byte[], char[] or business classes; 3. View the reference chain through "ListObjects>withincoming/outgoingreferences" to determine whether it is accidentally held; 4. Use "Pathto

The core workaround for encountering java.io.NotSerializableException is to ensure that all classes that need to be serialized implement the Serializable interface and check the serialization support of nested objects. 1. Add implementsSerializable to the main class; 2. Ensure that the corresponding classes of custom fields in the class also implement Serializable; 3. Use transient to mark fields that do not need to be serialized; 4. Check the non-serialized types in collections or nested objects; 5. Check which class does not implement the interface; 6. Consider replacement design for classes that cannot be modified, such as saving key data or using serializable intermediate structures; 7. Consider modifying

There are three common methods to traverse Map in Java: 1. Use entrySet to obtain keys and values at the same time, which is suitable for most scenarios; 2. Use keySet or values to traverse keys or values respectively; 3. Use Java8's forEach to simplify the code structure. entrySet returns a Set set containing all key-value pairs, and each loop gets the Map.Entry object, suitable for frequent access to keys and values; if only keys or values are required, you can call keySet() or values() respectively, or you can get the value through map.get(key) when traversing the keys; Java 8 can use forEach((key,value)->

ToimproveperformanceinJavaapplications,choosebetweenEhCacheandCaffeinebasedonyourneeds.1.Forlightweight,modernin-memorycaching,useCaffeine—setitupbyaddingthedependency,configuringacachebeanwithsizeandexpiration,andinjectingitintoservices.2.Foradvance

Dynamic web crawling can be achieved through an analysis interface or a simulated browser. 1. Use browser developer tools to view XHR/Fetch requests in the Network, find the interface that returns JSON data, and use requests to get it; 2. If the page is rendered by the front-end framework and has no independent interface, you can start the browser with Selenium and wait for the elements to be loaded and extracted; 3. In the face of the anti-crawling mechanism, headers should be added, frequency control, proxy IP should be used, and verification codes or JS rendering detection should be carried out according to the situation. Mastering these methods can effectively deal with most dynamic web crawling scenarios.
