Implement Stack Using Two Queues

A Stack follows LIFO (Last In First Out), while a Queue follows FIFO (First In First Out). We can implement a Stack using two Queues (Q1 and Q2) by making the Stack operations behave like LIFO.

Method (Costly Push / Easy Pop)

Idea: Always keep the newest element at the front of Q1, so that Pop works like Stack.

Operations:

1) Push(x):

• Enqueue x into Q2.
• Move all elements from Q1 to Q2 (dequeue from Q1 and enqueue to Q2).
• Swap Q1 and Q2 (now Q1 has the new order).

2) Pop():

• If Q1 is empty → Stack is empty.
• Dequeue from Q1 and return it (this is the top element).

3) Top/Peek():

• Return the front element of Q1.

4) isEmpty():

• If Q1 is empty → true, else false.

Time Complexity:

Push = O(n), Pop = O(1), Top = O(1)

Convert 10.12.2.0 – 10.12.3.255 to CIDR Notation

Step 1: Identify the Range

Starting IP: 10.12.2.0

Ending IP: 10.12.3.255

Step 2: Check the Third Octet

The range covers 10.12.2.0 to 10.12.3.255 → which means 2 continuous blocks (2 and 3).

Step 3: Count Total IP Addresses

Each Class C block (/24) contains 256 IPs.

Here we have 2 blocks → 256 × 2 = 512 IP addresses.

Step 4: Find CIDR Prefix

512 = 2⁹

Total bits in IPv4 = 32

32 − 9 = 23

Final Answer:

The CIDR notation is 10.12.2.0/23

Subnet Mask = 255.255.254.0

1. Multiplexer (MUX)

Multiplexer (MUX) is a combinational logic circuit that selects one input from multiple input lines and forwards it to a single output line.

It has n selection lines to choose one of 2ⁿ input lines. It is used to reduce the number of data lines and efficiently transmit data.

Example: A 4-to-1 MUX has 4 input lines, 2 select lines, and 1 output line.

2. Difference between D Flip-Flop and D Latch