SDE - 1

Approach :


I) Using Hashing :
Basically, we need to find a common node of two linked lists. So we hash all nodes of the first list and then check the second list.

Note : Hash the nodes not the node value

1) Create an empty hash set.
2) Traverse the first linked list and insert all nodes' addresses in the hash set.
3) Traverse the second list. For every node check if it is present in the hash set. If we find a node in the hash set, return the node

TC : O(m+n)
SC : O(min(m,n))

II) Using Two pointers :

1) Initialize two pointers ptr1 and ptr2 at the head1 and head2.
2) Traverse through the lists,one node at a time.
3) When ptr1 reaches the end of a list, then redirect it to the head2.
4) Similarly when ptr2 reaches the end of a list, redirect it the head1.
5) Once both of them go through reassigning, they will be equidistant from the collision point
6) If at any node ptr1 meets ptr2, then it is the intersection node.
7) After second iteration if there is no intersection node it returns NULL.

TC : O(m+n) where m=Length of LL-1 and n=Length of LL-2
SC : O(1)

Approach : I solved it using 2-pointers and keeping a track of the frequency of the elements encountered in a freq array of size 26.

Steps :
1) Initiliase a freq array of size 26 where a=0, b=1 ...,z=25 .
2) Let s be our string and n = s.size()
3) Do , freq[s[0]]++;
4) Keep 2 pointers start and end where initially start=0 and end=1 also maintain a answer variable ans where initially ans=0
5) Now run a loop till end=1 and start7) Update ans by ans=max(ans , end-start+1)
8) Finally return ans

TC : O(N)
SC : O(26)=O(1)

DNS is the Domain Name System. It is considered as the devices/services directory of the Internet. It is a decentralized and hierarchical naming system for devices/services connected to the Internet. It translates the domain names to their corresponding IPs.

MAC addresses and IP addresses operate on different layers of the internet protocol suite. MAC addresses are used to identify machines within the same broadcast network on layer 2, while IP addresses are used on layer 3 to identify machines throughout different networks.

Even if your computer has an IP address, it still needs a MAC address to find other machines on the same network (especially the router/gateway to the rest of the network/internet), since every layer is using underlying layers.

C++ is an Object-oriented programming language and it supports Polymorphism as well:

Compile Time Polymorphism: C++ supports compile-time polymorphism with the help of features like templates, function overloading, and default arguments.

Runtime Polymorphism: C++ supports Runtime polymorphism with the help of features like virtual functions. Virtual functions take the shape of the functions based on the type of object in reference and are resolved at runtime.

ARP is Address Resolution Protocol. It is a network-level protocol used to convert the logical address i.e. IP address to the device's physical address i.e. MAC address. It can also be used to get the MAC address of devices when they are trying to communicate over the local network.

1) The browser extracts the domain name from the URL.

2) The browser queries DNS for the IP address of the URL. Generally, the browser will have cached domains previously visited, and the operating system will have cached queries from any number of applications. If neither the browser nor the OS have a cached copy of the IP address, then a request is sent off to the system's configured DNS server. The client machine knows the IP address for the DNS server, so no lookup is necessary.

3) The request sent to the DNS server is almost always smaller than the maximum packet size, and is thus sent off as a single packet. In addition to the content of the request, the packet includes the IP address it is destined for in its header. Except in the simplest of cases (network hubs), as the packet reaches each piece of network equipment between the client and server, that equipment uses a routing table to figure out what node it is connected to that is most likely to be part of the fastest route to the destination. The process of determining which path is the best choice differs between equipment and can be very complicated.

4) The data is either lost (in which case the request fails or is reiterated), or makes it to its destination, the DNS server.

5) If that DNS server has the address for that domain, it will return it. Otherwise, it will forward the query along to DNS server it is configured to defer to. This happens recursively until the request is fulfilled or it reaches an authoritative name server and can go no further.

6) Assuming the DNS request is successful, the client machine now has an IP address that uniquely identifies a machine on the Internet. The web browser then assembles an HTTP request, which consists of a header and optional content. The header includes things like the specific path being requested from the web server, the HTTP version, any relevant browser cookies, etc.

7) This HTTP request is sent off to the web server host as some number of packets, each of which is routed in the same was as the earlier DNS query. (The packets have sequence numbers that allow them to be reassembled in order even if they take different paths.) Once the request arrives at the webserver, it generates a response (this may be a static page, served as-is, or a more dynamic response, generated in any number of ways.) The web server software sends the generated page back to the client.

This is what happens when we type Google.com on our browser.

Answer :
There are two main types of semaphores i.e. counting semaphores and binary semaphores.

1) Counting Semaphores :
These are integer value semaphores and have an unrestricted value domain. These semaphores are used to coordinate the resource access, where the semaphore count is the number of available resources. If the resources are added, semaphore count automatically incremented and if the resources are removed, the count is decremented.

2) Binary Semaphores :
The binary semaphores are like counting semaphores but their value is restricted to 0 and 1. The wait operation only works when the semaphore is 1 and the signal operation succeeds when semaphore is 0. It is sometimes easier to implement binary semaphores than counting semaphores.

Answer :
1) It is generally a situation where the CPU performs less productive work and more swapping or paging work.
2) It spends more time swapping or paging activities rather than its execution.
3) By evaluating the level of CPU utilization, a system can detect thrashing.
4) It occurs when the process does not have enough pages due to which the page-fault rate is increased. 5) It inhibits much application-level processing that causes computer performance to degrade or collapse.