SDE - 1

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.

Note :

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.

For Example :

()()()() is a valid parentheses.
)()()( is not a valid parentheses.

Design a data structure to implement a stack, using only deque (double-ended queue). It should support the following operations :

push(X): Pushes an element X into the stack. Returns true if the element is pushed into the stack, otherwise false.

pop(): Pops the top element from the stack. Returns -1 if the stack is empty, otherwise, returns the popped element.

top(): Returns the topmost element of the stack. In case the stack is empty, it returns -1.

isEmpty() : Returns true if the stack is empty, otherwise false.

size(): Returns the number of elements currently present in the stack.

Following type of queries denote these operations :

Type 1 : for push(X) operation.

Type 2 : for pop() operation.

Type 3 : for top() operation.

Type 4 : for isEmpty() operation.

Type 5 : for size() operation.

Given a singly linked list of 'N' nodes. The objective is to determine the middle node of a singly linked list. However, if the list has an even number of nodes, we return the second middle node.

Note:

1. If the list is empty, the function immediately returns None because there is no middle node to find.
2. If the list has only one node, then the only node in the list is trivially the middle node, and the function returns that node.

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