Therap

Introduction

Therap (BD) Ltd. is a US-based Software Company registered in Bangladesh, operating since 2004. They have their office in Dhaka, Bangladesh, and affiliate offices in the USA and Canada. Therap has multiple roles.

1. Software Engineer
2. Database Engineer
3. Quality Assurance Engineer
4. Embedded System Engineer

TIP

Therap BD organizes a Java fest every year. The prize money is very handsome. Apart from that, if you advance to final that means you get a direct ticket to interview skipping the initial screening

Interview Stages

The selection process generally has 3 steps

1. Initial screening: This round is taken in written format
2. 1st technical round The first round is taken by the BD team
3. 2nd technical round: This round is typically taken by the USA team

Database Questions

Design an ERD of online restaurant management system

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[Answer]

What is Database Transaction

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[Answer]

Briefly explain ACID properties

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ACID is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. Databases that support this are called ACID compliance. The properties are

• Atomicity: Each statement in a transaction (to read, write, update or delete data) is treated as a single unit. Either the entire statement is executed, or none of it is executed.
• Consistency: Ensures the databases remain consistent following some predefined business logic both before and after the transaction
• Isolation: Each transaction executes in such a way that one is not affected by other s though they were occurring only one.
• Durability: The data changes by a successfull transaction is saved even in the event of system failure

IMPORTANT

Atomicity, isolation and durability are properties of the database, whereas consistency is a property of the application. The C in ACID was tossed in to make the acronym work. [ref: Martin Kleppmann, Designing Data Intensive Applications]

What is normalization and denormalization

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[Answer]

Briefly explain BCNF

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[Answer]

Explain data warehousing

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[Answer]

Explain data redundancy

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[Answer]

Briefly mention the differences between stored procedure, function and trigger

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[Answer]

Briefly mention the differences between delete, drop and truncate

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[Answer]

Briefly mention the differences between where and having clause

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[Answer]

Briefly mention the differences between candidate key and super key

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[Answer]

A schema has entities like CUSTOMERS, ORDERS, ORDER_ITEMS, PRODUCTS, PRODUCT_DETAILS, WAREHOUSES, INVENTORIES. Data fields of entities and cardinality relationships were given in the figure. Questions included from <> 1. Group by, Order by, Join <> 2. Extracting month and year from oracle dates <> 3. Find ranks based on some criterion. The extremely hard question was - find top 10 customers based on their total amount spent in 2023. This one involved the following topics: aggregation, join of multiple tables, nested sub-query, year extraction from date. The book of Sukarna sir contains one/two such exercises. Practise them properly

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[Answer]

Software Engineering Questions

Given an array of numbers indicating stock price of n consecutive days. If you buy stock at one day and sell at any later day what is the maximum profit that you can get

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💻 Submit Code

int maxProfit(vector<int>& prices) {
    int buy = prices[0];
    int profit = 0;
    for(int i=1;i<prices.size();i++){
        if( prices[i]-buy > profit ) profit = prices[i] - buy;
        if( prices[i] < buy ) buy = prices[i];
    }
    return profit;
}

Given an array of n integers. You need to take all zeroes in array to the end without changing the relative order of remaining element. eg: [2,0,0,3,1,0,5] => [2,3,1,5,0,0,0]

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💻 Submit Code

void moveZeroes(vector<int>& nums) {
    int i = 0;
    for(int j=0;j<nums.size();j++){
        swap(nums[i], nums[j]);
        if( nums[i] != 0 ) i++;
    }
}

Given an array of n integers. Reorder the elements such that all odd numbers occur after even numbers.

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[Answer]

Given an array of strings. Print the sets of strings which are anagram. eg: ["cat","tab","act","bat","taco"] => [{"cat","act"},{"tab","bat"},{"taco"}]

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💻 Submit Code

vector<vector<string>> groupAnagrams(vector<string>& strs) {
    map<string,int> index;
    vector<vector<string>> vs;
    for(auto str:strs){
        string str2 = str;
        if( str2.size()>1 ) sort(str2.begin(),str2.end());
        if( index.find(str2) == index.end() ){
            vs.push_back(vector<string>());
            index[str2] = vs.size()-1;
        }
        vs[ index[str2] ].push_back(str);
    } 
    return vs;
}

Given an array of n integers. Find the kth largest element in the array.

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💻 Submit Code

int findKthLargest(vector<int>& nums, int k) {
    partial_sort(nums.begin(), nums.begin() + k, nums.end(), greater<int>());
    return nums[k-1];
}

Given two very large number in string format. Find the sum of the two number

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string sum(string &A, string &B){
    reverse(A.begin(),A.end());
    reverse(B.begin(),B.end());
    string sum;
    int c = 0;
    int i=0,j=0;
    while(true){
        int a=0,b=0;
        if( i<A.size() ) a = A[i++]-'0';
        if( j<B.size() ) b = B[j++]-'0';

        int s = (a+b+c)%10;
        c = (a+b+c)/10;
        sum.push_back(s+'0');
        if( i>=A.size() and j>=B.size() and c == 0 ) break;
    }
    reverse(sum.begin(),sum.end());
    return sum;
}

Given two binary tree. Check if they are identical [not isomorphism]

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💻 Submit Code

Normal Solution

bool isSameTree(TreeNode* p, TreeNode* q) {
    if( p == nullptr and q != nullptr ) return false;
    if( p != nullptr and q == nullptr ) return false;
    if( p == nullptr and q == nullptr ) return true;

    if( p->val != q->val ) return false;

    return isSameTree(p->left,q->left) && 
            isSameTree(p->right,q->right);
}

Weird Solution

// ref: https://go.dev/tour/concurrency/7
package main

import (
	"fmt"

	"golang.org/x/tour/tree"
)

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func WalkRecursive(t *tree.Tree, ch chan int) {
	if t.Left != nil {
		WalkRecursive(t.Left, ch)
	}
	ch <- t.Value
	if t.Right != nil {
		WalkRecursive(t.Right, ch)
	}
}

func Walk(t *tree.Tree, ch chan int) {
    WalkRecursive(t, ch)
    close(ch)
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
	ch1 := make(chan int)
	ch2 := make(chan int)
	go Walk(t1, ch1)
	go Walk(t2, ch2)
	for {
		x, ok1 := <-ch1
		y, ok2 := <-ch2

		if ok1 != ok2 || x != y {
			return false
		}
		if !ok1 {
			break
		}
	}
	return true
}

func main() {
	fmt.Println(Same(tree.New(1), tree.New(2)))
}

Given two array of integers. Find the common elements between them.

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💻 Submit Code Unique
💻 Submit Code Repeats

Return uniques

vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
    set<int> st;
    for(auto num:nums1) st.insert(num);
    set<int> res;
    for(auto num:nums2) if( st.count(num) == 1 ) res.insert(num);
    vector<int> ret;
    for(auto num:res) ret.push_back(num);
    return ret;
}

With repeatation

vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
    sort(nums1.begin(),nums1.end());
    sort(nums2.begin(),nums2.end());

    vector<int> merged;
    int i=0,j=0;
    while(i<nums1.size() and j<nums2.size()){
        if( nums1[i] == nums2[j] ){
            merged.push_back(nums1[i]);
            i++;j++;
        }else if( nums1[i]<nums2[j] ) i++;
        else j++;
    }
    return merged;
}

Find pairs with given target sum in a doubly linked list. Input: 1 <> 2 <> 4 <> 5 <> 6 <> 8 <> 9 target = 7 Output: (1,6), (2,5)

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💻 Submit Code

class Solution
{
public:
    vector<pair<int, int>> findPairsWithGivenSum(Node *head, int target)
    {
        vector<pair<int,int>> ans;
        
        Node* left = head;
        
        /// traverse to the end of the list
        while(head!= nullptr && head->next!=nullptr){
            head = head->next;
        }
        Node* right = head;
        
        while(left!= right && left->prev != right){
            if(left->data + right->data == target){
                ans.push_back(make_pair(left->data, right->data));
                left = left->next;
                right = right->prev;
            }
            else if(left->data + right->data > target){
                right = right->prev;
            }else{
                left = left->next;
            }
        }
        
        return ans;    
        
    }
};

Solve the problem using Object Oriented Programming

int main(){
    int square1width = 50;
    int square2width = 80;
    int rectangle1width = 30, rectangle1height = 40;
    int rectangle2width = 20, rectangle2height = 40;

    int square1area = square1width* square1width;
    int square2area = square2width* square2width;
    int rectangle1area = rectangle1height*rectangle1width;
    int rectangle2area = rectangle2width* rectangle2height;
}

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#include <iostream>
using namespace std;

// Abstract base class
class Shape {
public:
    virtual int area() const = 0;  // Pure virtual function for area
};

class Square : public Shape {
private:
    int width;
public:
    Square(int w) : width(w) {}  // Constructor to initialize width

    int area() const override {
        return width * width;  // Area of square
    }
};

class Rectangle : public Shape {
private:
    int width;
    int height;
public:
    Rectangle(int w, int h) : width(w), height(h) {}  // Constructor to initialize width and height

    int area() const override {
        return width * height;  // Area of rectangle
    }
};

int main() {
    
    Square square1(50);
    Square square2(80);
    Rectangle rectangle1(30, 40);
    Rectangle rectangle2(20, 40);

    cout << "Square 1 area: " << square1.area() << endl;
    cout << "Square 2 area: " << square2.area() << endl;
    cout << "Rectangle 1 area: " << rectangle1.area() << endl;
    cout << "Rectangle 2 area: " << rectangle2.area() << endl;
    return 0;
}