SDE - 1

Implement a Stack Data Structure specifically to store integer data using two Queues.

There should be two data members, both being Queues to store the data internally. You may use the inbuilt Queue.

Implement the following public functions :

1. Constructor:
It initializes the data members(queues) as required.

2. push(data) :
This function should take one argument of type integer. It pushes the element into the stack and returns nothing.

3. pop() :
It pops the element from the top of the stack and, in turn, returns the element being popped or deleted. In case the stack is empty, it returns -1.

4. top :
It returns the element being kept at the top of the stack. In case the stack is empty, it returns -1.

5. size() :
It returns the size of the stack at any given instance of time.

6. isEmpty() :
It returns a boolean value indicating whether the stack is empty or not.

Operations Performed on the Stack:

Query-1(Denoted by an integer 1): Pushes an integer data to the stack. (push function)

Query-2(Denoted by an integer 2): Pops the data kept at the top of the stack and returns it to the caller. (pop function)

Query-3(Denoted by an integer 3): Fetches and returns the data being kept at the top of the stack but doesn't remove it, unlike the pop function. (top function)

Query-4(Denoted by an integer 4): Returns the current size of the stack. (size function)

Query-5(Denoted by an integer 5): Returns a boolean value denoting whether the stack is empty or not. (isEmpty function)

Example

Operations: 
1 5
1 10
2
3
4

Enqueue operation 1 5: We insert 5 at the back of the queue.
  Queue: [5]

Enqueue operation 1 10: We insert 10 at the back of the queue.
  Queue: [5, 10]

Dequeue operation 2: We remove the element from the front of the queue, which is 5, and print it.
  Output: 5
  Queue: [10]

Peek operation 3: We return the element present at the front of the queue, which is 10, without removing it.
  Output: 10
  Queue: [10]

IsEmpty operation 4: We check if the queue is empty.
  Output: False
  Queue: [10]

You are given a matrix 'MAT' of size ‘N’ * ‘M’, where ‘N’ is the number of rows and ‘M’ is the number of columns. Value ‘0’ in a cell represents that the cell is set on fire initially, (at time t = ‘0’), and the cells which don’t have fire initially have value = ‘1’, and are called safe cells.

If a cell is on fire, then in one second the fire will expand to its adjacent cells (left, right, top, bottom) if they are not already on fire.

You are given the position of a person as integers ‘X’ and ‘Y’ denoting the cell (‘X’, ‘Y’). In one second the person can move from its current cell to any one of its adjacent cells, provided they are not on fire.

You have to determine if the person can move through the matrix to one of the escape cells without burning himself i.e. without going through the fire cells. If it’s possible, return time taken, else return -1.

Note:

1. Escape cells in this problem are all such cells that lie on the edge of the matrix but not on the corner. i.e all such cells which are in the first row, first column, last row, and last column excluding the four corner cells are considered as valid escape cells.

2. A cell once set on fire continues to remain on fire till the end.

3. Note that rows are indexed from 0 to ‘N’ - 1 and columns are indexed from 0 to ‘M’ - 1.

4. The escape cells may also be initially on fire or can catch fire from some neighboring cell.

You are given the first term (A), the common ratio (R) and an integer N. Your task is to find the Nth term of the GP series.

The general form of a GP(Geometric Progression) series is A, A(R), A(R^2), A*(R^3) and so on where A is the first term of GP series

Note :

As the answer can be large enough, return the answer modulo 10^9 + 7.

You are given a binary tree consisting of 'n' nodes.

Convert the given binary tree into a linked list where the linked list nodes follow the same order as the pre-order traversal of the given binary tree.

Use the right pointer of the binary tree as the “next” pointer for the linked list and set the left pointer to NULL.

Use these nodes only. Do not create extra nodes.

Example :

Input: Let the binary be as shown in the figure:

Output: Linked List: 15 -> 40 -> 62 -> 10 -> 20 -> NULL

Explanation: As shown in the figure, the right child of every node points to the next node, while the left node points to null.

Also, the nodes are in the same order as the pre-order traversal of the binary tree.

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