# PUPPALA HARIKA | 4+ yrs exp | R2
-
- Nodejs, Javascript
- MySQL, Redis
- AWS: Kafka, S3, IAM, RDS, KMS

# Question 1: Js problem

const nestedObj = {
    a: "Hi",
    b: { c: "Hello", g: {h: "World"}},
    d: { e: { f: 2} }
}
// const flattenObj = {
//     a: "Hi",
//     b_c: "Hello",
//     b_g_h: "World",
//     d_e_f: 2
// }


function flattenObject(nestedObj){
    const res ={};
    for(const i in nestedObj){
        if((typeof nestedObj[i]) ==="object" && nestedObj[i]!== null){
            const flatObj= flattenObject(nestedObj[i]);
            for(const j in flatObj){
                if(!flatObj.hasOwnProperty(j)) continue;
                res[i+'_'+j] = flatObj[j];
            }
        }else{
            res[i] = nestedObj[i];
        }
    }
    
    return res;
}


const result = flattenObject(nestedObj);
console.log(result);

# Question 2:

- Array [1, 2, 3, 4, 5] (distinct)
k = 3 , 0<k<array.length

[1, 2, 3]
[1, 2, 4]
[1, 2, 5]
[1, 3, 4]
[1, 3, 5]
....

function combinations(arr, k){
    let result =[]
    function getCombinations(start, curr){
        if(curr.length===k){
            result.push([...curr]);
            return
        }
        let prev = null;
        for(let i=start;i<arr.length;i++){
            if(prev!== arr[i]){
                curr.push(arr[i]);
                getCombinations(i+1, curr);
                curr.pop();
                prev = arr[i];
            }
        }
    }
    
    arr.sort((a,b)=> a-b);
    getCombinations(0,[]);
    return result;
    
}
let arr = [1, 2, 3, 4, 5];
console.log(combinations(arr, 3));

# Question 3: Kafka Usecases
- Throughput
- Retention

Kafka
------
Topics
Producer()
consumer()

Topic:

Will take a array/queue and when new messages arrive , we will append to queue.

Producer:

Class KafkaProducer{
constructor(){
this.topics={};
}

createTopic(topicName){
if(!this.topics[topicName]){
this.topics[topicName] =[]
}

}

produce(topicName, message){
if(!this.topics[topicName]){
console.warn("topic is not prent , create ")
this.createTopic(topicName)
}
// push messages to that topic
this.topics[topicName].push(message);
}

printMessage(topicName){
// put some logic to print it
}
}

Consumer :
1. subscribe
2. consume

Class KafkaConsumer{
constructor(kafka, groupId){
this.kafka = kafka;
this.groupId = groupId;
this.offset = {};
}

subscribe(topicName){
if(!this.offset[topicName]){
this.offset[topicName]=0;
}
}

consume(topicName){
if(!this.kafka.topics[topicName]){
console.warn("topic is not prent , create ")
return;
}

const messages = this.kafka.topics[topicName]
const newMessage = messages.slice(this.offset[topicName]);
if(newMessage.length===0){
console.log("no messages in the ${topicName } for this groupig")
return
}
// updating offset to latest
this.offset[topicName] += newMessage.length

}

}

const kafka = new KafkaProducer();
kafka.createTopic("topic1");
kafka.produce("topic1", {id:1, text : "Hi sample message"});

const consumerA = new KafkaConsumer();
consumerA

# Question 4:

25 Horses

Fastest 3 horse.
5 horse in a race.

1. lets assume 5 races
2. race between winners of each grp against each other = winner is the fastest of all
3. try to discard remaining : all horses in the grp where overall fastest is present , exccept the top two .
4. try to discard remaining: bottom 2 horses of grp that second fastest is present .
5. try to discard remaining:all horses in the grp where 3 fastest is present, except for 2 place.
6. try to discard remaining: all horses the fourth and fifth placed grps

top 2 of fastest, winner from second and third, second place from third = 5 horses

7. race these 5 horses , you will toable to get first , second, third ranked horses.

A,B,C,D,E

A1> 2
B1> (A1,A2,B1)
C1> (A1,A2,B1)
D1
E1

A1, A2, B1, B2, C1, C2

B2< A2 (B1<A1)
A2, B1, B2, C1, C2 - RACE
A2> B1> C1> B2>C2 - RESULT