diff --git a/Exercise_1.py b/Exercise_1.py
index 532833f5d..5da7108e3 100644
--- a/Exercise_1.py
+++ b/Exercise_1.py
@@ -1,20 +1,42 @@
+# Time Complexity : 
+# isEmpty: O(1)
+# push: O(1)
+# pop: O(1)
+# peek: O(1)
+# size: O(1)
+# show: O(n)
+# Space Complexity : Space Complexity is O(n)
+# Did this code successfully run on Leetcode : Solved minstack successfully, The minStack needs to be traversed with the help of 
+# Any problem you faced while coding this : None.
 class myStack:
   #Please read sample.java file before starting.
   #Kindly include Time and Space complexity at top of each file
      def __init__(self):
+          self.stack = []
          
      def isEmpty(self):
+          return len(self.stack) == 0
          
      def push(self, item):
+          self.stack.append(item)
          
      def pop(self):
+          if self.isEmpty():
+              return print("Stack Empty")
+          return self.stack.pop()
         
         
      def peek(self):
+          if self.isEmpty():
+               return print("Stack Empty")
+          return self.stack[-1]
+          
         
      def size(self):
+          return len(self.stack)
          
      def show(self):
+          return self.stack
          
 
 s = myStack()
diff --git a/Exercise_2.py b/Exercise_2.py
index b11492215..3b5b4451f 100644
--- a/Exercise_2.py
+++ b/Exercise_2.py
@@ -1,4 +1,8 @@
-
+# Time Complexity : 
+# push: O(1)
+# pop: O(1)
+# Space Complexity : O(n)
+# Any problem you faced while coding this : None
 class Node:
     def __init__(self, data):
        self.data = data
@@ -6,10 +10,19 @@ def __init__(self, data):
  
 class Stack:
     def __init__(self):
+        self.top = None
         
     def push(self, data):
+        newNode = Node(data)
+        newNode.next = self.top
+        self.top = newNode
         
     def pop(self):
+        if self.top is None:
+            return None
+        res = self.top.data
+        self.top = self.top.next
+        return res
         
 a_stack = Stack()
 while True:
diff --git a/Exercise_3.py b/Exercise_3.py
index a5d466b59..4475b86c4 100644
--- a/Exercise_3.py
+++ b/Exercise_3.py
@@ -1,8 +1,14 @@
+# Time Complexity :
+# Space Complexity :
+# Did this code successfully run on Leetcode :
+# Any problem you faced while coding this :
 class ListNode:
     """
     A node in a singly-linked list.
     """
     def __init__(self, data=None, next=None):
+        self.data = data
+        self.next = next
     
 class SinglyLinkedList:
     def __init__(self):
@@ -17,6 +23,12 @@ def append(self, data):
         Insert a new element at the end of the list.
         Takes O(n) time.
         """
+        New_Node = ListNode(data)
+        curr = self.head
+        while curr.next:
+            curr = curr.next
+        
+        curr.next = New_Node
         
     def find(self, key):
         """
@@ -24,9 +36,24 @@ def find(self, key):
         `key`. Return the element or `None` if not found.
         Takes O(n) time.
         """
+        curr = self.head
+
+        while curr.next:
+            if curr.data == key:
+                return curr
+            curr = curr.next
+        return None
         
     def remove(self, key):
         """
         Remove the first occurrence of `key` in the list.
         Takes O(n) time.
         """
+
+        curr = self.head
+
+        while curr.next and curr.next.next:
+            if curr.next.val == key:
+                curr.next = curr.next.next
+                break
+            curr = curr.next