Tip 1 : Practice more problem solving questions
Tip 2 : understand the comcepts in depth
Tip 3 : try to work on onw or two handson project to get more experience in that stack.
Tip 1 : Have some projects on resume.
Tip 2 : Do not put false things on resume.



Conditions for valid parentheses:
1. All open brackets must be closed by the closing brackets.
2. Open brackets must be closed in the correct order.
()()()() is a valid parentheses.
)()()( is not a valid parentheses.
Given an integer ‘N’ representing the number of pairs of parentheses, Find all the possible combinations of balanced parentheses with the given number of pairs of parentheses.



Input:
'num1' : 1 -> 2 -> 3 -> NULL
'num2' : 4 -> 5 -> 6 -> NULL
Output: 5 -> 7 -> 9 -> NULL
Explanation: 'num1' represents the number 321 and 'num2' represents 654. Their sum is 975.
You are given two linked lists representing two non-negative numbers. The digits in the linked list are stored in reverse order, i.e. starting from least significant digit (LSD) to the most significant digit (MSD), and each of their nodes contains a single digit. Your task is to find the sum list and return the head of the sum list where the sum list is a linked list representation of the addition of two numbers.



1. Push(num): Push the given number in the stack if the stack is not full.
2. Pop: Remove and print the top element from the stack if present, else print -1.
3. Top: Print the top element of the stack if present, else print -1.
4. isEmpty: Print 1 if the stack is empty, else print 0.
5. isFull: Print 1 if the stack is full, else print 0.
We perform the following operations on an empty stack which has capacity 2:
When operation 1 1 is performed, we insert 1 in the stack.
When operation 1 2 is performed, we insert 2 in the stack.
When operation 2 is performed, we remove the top element from the stack and print 2.
When operation 3 is performed, we print the top element of the stack, i.e., 3.
When operation 4 is performed, we print 0 because the stack is not empty.
When operation 5 is performed, we print 0 because the stack is size 1, which is not equal to its capacity.
You need to implement the Stack data structure using a Singly Linked List.
Create a class named 'Stack' which supports the following operations(all in O(1) time):



Input: Given linked list is:

Output:
1 → 2 → 3 → 4 → 5 → 6 → 7 → 8 → 9 → 12 → 20 → null.
Explanation:
The returned linked list should be in a sorted order. All the elements in this returned linked list are connected by 'child' pointers and 'next' pointers point to null.
You are given a linked list containing N nodes, where every node in the linked list contains two pointers, first one is ‘NEXT’ which points to the next node in the list and the second one is ‘CHILD’ pointer to a linked list where the head is this node. And each of these child linked lists is in sorted order.
Your task is to flatten this linked such that all nodes appear in a single layer or level while the nodes should maintain the sorted order.
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