The peek operation in a stack involves viewing the element at the top of the stack without removing it. This operation allows us to access the top element while keeping the stack intact. Stacks follow a Last In, First Out (LIFO) principle, meaning the most recently added element is at the top of the stack.

Consider a stack with the following structure before the peek operation:

```
Stack (Top -> Bottom):
Top -> 4 -> 3 -> 2 -> 1
```

To peek the top element of the stack, follow these steps:

**Check if the Stack is Empty**: If the stack is empty, return an error or None.**Return the Top Node's Value**: Return the value of the top node.

After performing these steps, the stack remains unchanged:

```
Stack (Top -> Bottom):
Top -> 4 -> 3 -> 2 -> 1
```

```
Function peek(stack):
# Check if the stack is empty
If stack.top is null:
Return None
# Return the value of the top node
Return stack.top.data
```

```
class Node:
def __init__(self, data):
self.data = data
self.next = None
class Stack:
def __init__(self):
self.top = None
def push(self, data):
# Create a new node with the given data
new_node = Node(data)
# Set the new node's next reference to the current top of the stack
new_node.next = self.top
# Update the top reference to the new node
self.top = new_node
def pop(self):
# Check if the stack is empty
if self.top is None:
return None
# Store the current top node
temp = self.top
# Update the top reference to the next node
self.top = self.top.next
# Return the value of the stored top node
return temp.data
def peek(self):
# Check if the stack is empty
if self.top is None:
return None
# Return the value of the top node
return self.top.data
def traverse(self):
# Traverse and print the stack
current = self.top
while current:
print(current.data, end=" -> ")
current = current.next
print("None")
# Example usage:
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
stack.push(4)
print("Stack before peeking:")
stack.traverse() # Output: 4 -> 3 -> 2 -> 1 -> None
peeked_element = stack.peek()
print(f"Peeked element: {peeked_element}") # Output: 4
print("Stack after peeking:")
stack.traverse() # Output: 4 -> 3 -> 2 -> 1 -> None
```

This Python program defines a stack with methods for pushing elements onto the stack, popping elements from the stack, peeking at the top element of the stack, and traversing the stack. The peek method checks if the stack is empty and returns the value of the top node without modifying the stack.