Homework: C# Advanced Topics This document defines the homework assignments from the “C# Basics“ Course @ Software University.

Problem 1. Fibonacci Numbers Define a method Fib(n) that calculates the nth Fibonacci number. Examples: n Fib(n) 0 1 1 1 2 2 3 3 4 5 5 8 6 13 11 144 25 121393

Problem 2. Prime Checker Write a Boolean method IsPrime(n) that check whether a given integer number n is prime. Examples: n IsPrime(n) 0 false 1 false 2 true 3 true 4 false 5 true 323 false 337 true 6737626471 true 117342557809 false

Problem 3. Primes in Given Range Write a method that calculates all prime numbers in given range and returns them as list of integers: static List FindPrimesInRange(startNum, endNum) { … } Write a method to print a list of integers. Write a program that enters two integer numbers (each at a separate line) and prints all primes in their range, separated by a comma. Examples: Start number End number Output 0 10 2, 3, 5, 7 5 11 5, 7, 11 100 200 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199 250 950 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947 100 50 (empty list)

Problem 4. Difference between Dates Write a program that enters two dates in format dd.MM.yyyy and returns the number of days between them. Examples: First date Second date Days between 17.03.2014 30.04.2014 44 17.03.2014 17.03.2014 0 14.06.1980 5.03.2014 12317 5.03.2014 3.03.2014 -2

Problem 5. Sorting Numbers Write a program that reads a number n and a sequence of n integers, sorts them and prints them. Examples: Input Output 5 3 -3 2 122 0 -3 0 2 3 122 3 0 1 0 0 0 1

Problem 6. Longest Area in Array Write a program to find the longest area of equal elements in array of strings. You first should read an integer n and n strings (each at a separate line), then find and print the longest sequence of equal elements (first its length, then its elements). If multiple sequences have the same maximal length, print the leftmost of them. Examples: Input Output 6 hi hi hello ok ok ok 3 ok ok ok 2 SoftUni Hello 1 SoftUni 4 hi hi hi hi 4 hi hi hi hi 5 wow hi hi ok ok 2 hi hi

Problem 7. Matrix of Palindromes Write a program to generate the following matrix of palindromes of 3 letters with r rows and c columns: Input Output 3 6 aaa aba aca ada aea afa bbb bcb bdb beb bfb bgb ccc cec cdc cfc cgc chc 2 3 aaa aba aca bbb bcb bdb 1 1 aaa 1 3 aaa aba aca

Problem 8. * Longest Non-Decreasing Subsequence Write a program that reads a sequence of integers and finds in it the longest non-decreasing subsequence. In other words, you should remove a minimal number of numbers from the starting sequence, so that the resulting sequence is non-decreasing. In case of several longest non-decreasing sequences, print the leftmost of them. The input and output should consist of a single line, holding integer numbers separated by a space. Examples: Input Output 1 1 7 3 5 8 -1 6 7 3 5 6 7 1 1 1 2 2 2 1 1 1 1 1 1 3 3 3 2 2 2 2 2 2 2 2 11 12 13 3 14 4 15 5 6 7 8 7 16 9 8 3 4 5 6 7 8 9

Problem 9. Remove Names Write a program that takes as input two lists of names and removes from the first list all names given in the second list. The input and output lists are given as words, separated by a space, each list at a separate line. Examples: Input Output Peter Alex Maria Todor Steve Diana Steve Todor Steve Nakov Peter Alex Maria Diana Hristo Hristo Nakov Nakov Petya Nakov Vanessa Maria Hristo Hristo Petya

Problem 10. Join Lists Write a program that takes as input two lists of integers and joins them. The result should hold all numbers from the first list, and all numbers from the second list, without repeating numbers, and arranged in increasing order. The input and output lists are given as integers, separated by a space, each list at a separate line. Examples: Input Output 20 40 10 10 30 80 25 20 40 30 10 10 20 25 30 40 80 5 4 3 2 1 6 3 2 1 2 3 4 5 6 1 1 1

Problem 11. Count of Letters Write a program that reads a list of letters and prints for each letter how many times it appears in the list. The letters should be listed in alphabetical order. Use the input and output format from the examples below. Examples: Input Output b b a a b a -> 2 b -> 3 h d h a a a s d f d a d j d s h a a a -> 6 d -> 5 f -> 1 h -> 3 j -> 1 s -> 2

Problem 12. Count of Names Write a program that reads a list of names and prints for each name how many times it appears in the list. The names should be listed in alphabetical order. Use the input and output format from the examples below. Examples: Input Output Peter Steve Nakov Steve Alex Nakov Alex -> 1 Nakov -> 2 Peter -> 1 Steve -> 2 Nakov Nakov Nakov SoftUni Nakov SoftUni -> 1 Nakov -> 5

Problem 13. Average Load Time Calculator We have a report that holds dates, web site URLs and load times (in seconds) in the same format like in the examples below. Your tasks is to calculate the average load time for each URL. Print the URLs in the same order as they first appear in the input report. Print the output in the format given below. Use double floating-point precision. Examples: Input Output 2014-Mar-02 11:33 http://softuni.bg 8.37725 2014-Mar-02 11:34 http://www.google.com 1.335 2014-Mar-03 21:03 http://softuni.bg 7.25 2014-Mar-03 22:00 http://www.google.com 2.44 2014-Mar-03 22:01 http://www.google.com 2.45 2014-Mar-03 22:01 http://www.google.com 2.77 http://softuni.bg -> 7.813625 http://www.google.com -> 2.24875

2014-Apr-01 02:01 http://softuni.bg 8.37725 2014-Apr-01 02:05 http://www.nakov.com 11.622 2014-Apr-01 02:06 http://softuni.bg 4.33 2014-Apr-01 02:11 http://www.google.com 1.94 2014-Apr-01 02:11 http://www.google.com 2.011 2014-Apr-01 02:12 http://www.google.com 4.882 2014-Apr-01 02:34 http://softuni.bg 4.885 2014-Apr-01 02:36 http://www.nakov.com 10.74 2014-Apr-01 02:36 http://www.nakov.com 11.75 2014-Apr-01 02:38 http://softuni.bg 3.886 2014-Apr-01 02:44 http://www.google.com 1.04 2014-Apr-01 02:48 http://www.google.com 1.4555 2014-Apr-01 02:55 http://www.google.com 1.977 http://softuni.bg -> 5.3695625 http://www.nakov.com -> 11.3706666666667 http://www.google.com -> 2.21758333333333

Problem 14. Longest Word in a Text Write a program to find the longest word in a text. Examples: Input Output Welcome to the Software University. University The C# Basics course is awesome start in programming with C# and Visual Studio. programming

Problem 15. Extract URLs from Text Write a program that extracts and prints all URLs from given text. URL can be in only two formats: • http://something, e.g. http://softuni.bg, http://forums.softuni.bg, http://www.nakov.com • www.something.domain, e.g. www.nakov.com, www.softuni.bg, www.google.com Examples: Input Output The site nakov.com can be access from http://nakov.com or www.nakov.com. It has subdomains like mail.nakov.com and svetlin.nakov.com. Please check http://blog.nakov.com for more information. http://nakov.com www.nakov.com http://blog.nakov.com

Problem 16. * Counting a Word in a Text Write a program that counts how many times a given word occurs in given text. The first line in the input holds the word. The second line of the input holds the text. The output should be a single integer number – the number of word occurrences. Matching should be case-insensitive. Note that not all matching substrings are words and should be counted. A word is a sequence of letters separated by punctuation or start / end of text. Examples: Input Output hi Hidden networks say “Hi” only to Hitachi devices. Hi, said Matuhi. HI! 3 SoftUni The Software University (SoftUni) trains software engineers, gives them a profession and a job. Visit us at http://softuni.bg. Enjoy the SoftUnification at SoftUni.BG. Contact us.Email: INFO@SOFTUNI.BG. Facebook: https://www.facebook.com/SoftwareUniversity. YouTube: http://www.youtube.com/SoftwareUniversity. Google+: https://plus.google.com/+SoftuniBg/. Twitter: https://twitter.com/softunibg. GitHub: https://github.com/softuni 5 SoftUni Software University 0 SoftUni SoftUni 1 SoftUni SoftUni.SoftUni 2

Problem 17. * Perimeter and Area of Polygon Write a program that calculates the perimeter and the area of given polygon (not necessarily convex) consisting of n floating-point coordinates in the 2D plane. Print the result rounded to two decimal digits after the decimal point. Use the input and output format from the examples. To hold the points, define a class Point(x, y). To hold the polygon use a Polygon class which holds a list of points. Find in Internet how to calculate the polygon perimeter and how to calculate the area of a polygon. Examples: Input Output Comments 3 0 0 0 1 1 1 perimeter = 3.41 area = 0.50 7 -2 1 1 3 5 1 1 2 1 1 3 -2 -2 1 perimeter = 22.64 area = 9.5

Exam problems.** All of the problems below are given from Variant 8 of C# Basics Practical Exam (14 April 2014 Evening). You can submit your solutions HERE. You are not obligated to submit any of them in your homework. We highly recommend you to try solving some or all of them so you can be well prepared for the upcoming exam. You need to learn how to use conditional statements, loops, arrays and other things (learn in internet how or read those chapters in the book “Fundamentals of computer programming with C#”). If you still find those problems too hard for solving it’s very useful to check and understand the solutions. You can download all solutions and tests for this variant here or check all previous exams (scroll down to the bottom of the page). You can also test your solutions in our automated judge system to see if you pass all tests.

Problem 18. ** – Inside the Building

In Absurdistan the buildings look like the figure on the right. They consist of 6 blocks of size h * h. Their bottom-left corner is located at the coordinates (0, 0). See the figure (for h = 2) to get a better idea. Write a program that enters a size h and 5 points {x1, y1}, {x2, y2}, {x3, y3}, {x4, y4}, and {x5, y5} and prints for each of the points whether it is inside or outside of the building. Points at the building's border, like {0, 0}, are considered inside. Input The input data should be read from the console. • At the first line an integer number h specifying the size of the building will be given. • At the next 10 lines the numbers x1, y1, x2, y2, x3, y3, x4, y4, x5, y5 are given. The input data will always be valid and in the format described. There is no need to check it explicitly. Output The output should be printed on the console. It should consist of exactly 5 lines. At each line print either "inside" or "outside" depending of where each of the 5 input points are located. Constraints • All numbers in the input will be integers in the range [-1000 … 1000]. • Allowed working time for your program: 0.1 seconds. • Allowed memory: 16 MB. Examples Input Output Comments Input Output Comments 2 3 10 0 6 2 2 3 1 6 0 outside outside inside inside inside 15 29 38 37 19 30 0 -4 7 13 57 inside outside inside outside outside

Problem 19. ** – Student Cables Once at the Software University (SoftUni) we had problems with the Wi-Fi network. It was working well in the previous days even with a few hundred students browsing Internet in the same time, but at the exam all the students came with their laptop at fixed time and tried to establish a wireless connection simultaneously. This flooded the Wi-Fi access points and as a result some of the students were unable to get an IP address from the DHCP server. They of course established a Wi-Fi Internet connection after a few reconnects in next 5-10 minutes, but were highly stressed because they didn't had Internet immediately before the start the exam start. Nakov, the main driver of SoftUni, decided to solve the problem by connecting some of the students through a standard network cables. He installed a few network switches in the exam lab and started to prepare cables for the students. His idea was to use 5 meters long cables (called student cables) between the switches and the student's laptops. Nakov wanted to create as much as possible cables of size 5 meters. He had a lot of cables of different sizes, e.g. a big roll of 300 meters, another big roll of 130 meters and a few small cables of 30 cm, 15 cm and 10 cm. The cables had different sizes and was measured in different measures (meters or centimeters). Nakov calculated that he needed 2 cm for crimping each RJ45 connector and 3 cm for joining each two pieces of cable. It was complex to calculate how much cables Nakov can create so he needs your help. Write a program that takes as an input a sequence of N cables of different sizes and calculates how many student cables Nakov can create by first joining them all together, then cut them into 5 meters and 4 cm, and finally crimp the RJ45 connectors to obtain 5 meters long student network cables. Calculate also the length of the unused remaining cable. Note that cables shorter than 20 cm in the input will be thrown away, so please discard therm. Input The input data should be read from the console. • At the first line an integer number n specifying the number of cables will be given. • At the next 2 * n lines the cables will be given: first comes the cable length; second comes the measure. The input data will always be valid and in the format described. There is no need to check it explicitly. Output The output should be printed on the console. It should consist of exactly 2 lines: • The first line should hold the number of student cables. • The second line should hold the length of the remaining cable. Constraints • The number n will be integer in the range [1 … 100]. • The cable length is integer in the range [1 … 500]. • The cable measure is one of the following values: meters, centimeters. • Allowed working time for your program: 0.1 seconds. Allowed memory: 16 MB. Examples Input Output Comments Input Output 4 11 meters 18 centimeters 8 meters 120 centimeters 3 502 We have 4 cables: 1100 cm, 18 cm, 800 cm and 120 cm. The 18 cm cable is too short (18 cm < 20 cm), so it is discarded. We join 1100 cm + 800 cm + 120 cm and we lose 2*3 = 6 cm. We obtain 2014 cm joined cable. We create 3 student cables: 3 * (5 m cable + 2 cm RJ crimp + 2 cm RJ crimp) = 3 * 504 = 1512 cm. The remainder is 2014 – 1512 = 502 cm. 3 116 centimeters 4 meters 20 centimeters 1 26

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Problem 20. ** – Programmer DNA The secret scientists from the institute of Bizarre Artificial Neurobiology or B.A.N have tried for years to find the DNA markers of the perfect programmer. The work is going well but after an incident with the printer in the institute it is impossible to print the latest discovery. That is why they have asked you to help them. Your task is to make a program that can print simple DNA chains of various lengths. Simple DNA chains consist of sequence of diamond blocks containing only letters from A to G (see the example on the right). Letters are chained alphabetically: A is followed by B, then C, D, E, F, G, then again A and so on. Each DNA block is with size 7. Input The input data should be read from the console. • On the first line an integer number N specifying the length of the DNA chain will be given. • On the second line the starting letter of the chain will be given (capital letter from A to G). The input data will always be valid and in the format described. There is no need to check it explicitly. Output The output should be printed on the console. Following the examples below print exactly N lines of the programmer's DNA. Use only capital letters from A to G and “.” for the empty space. Constraints • N will always be a positive number between 7 and 999 inclusive. • Allowed working time for your program: 0.1 seconds. • Allowed memory: 16 MB. Examples Input Output Input Output 7 B ...B... ..CDE.. .FGABC. DEFGABC .DEFGA. ..BCD.. ...E... 10 F ...F... ..GAB.. .CDEFG. ABCDEFG .ABCDE. ..FGA.. ...B... ...C... ..DEF.. .GABCD.

Problem 21. ** – Magic Car Numbers Cars in Sofia have registration numbers in format "CAabcdXY" where a, b, c and d are digits from 0 to 9 and X and Y are letters from the following subset of the Latin alphabet: 'A', 'B', 'C', 'E', 'H', 'K', 'M', 'P', 'T' and 'X'. Examples of car numbers from Sofia are "CA8517TX", "CA2277PC", "CA0710XC", "CA1111AC", while "CC7512FJ" in not valid car number from Sofia. Local people are keen to choose special numbers for their cars, know as magic car numbers. They calculate the weight of a car number as follows: they sum its digits and letters, assuming that letters have the following values: 'A'  10, 'B'  20, 'C'  30, 'E'  50, 'H'  80, 'K'  110, 'M'  130, 'P'  160, 'T'  200, 'X'  240. For example the weight("CA6511BM") = 30 + 10 + 6 + 5 + 1 + 1 + 20 + 130 = 203. A magic car number is a car number that has a special magic weight (e.g. 256 or 512 for developers) and its number is in some of the formats "CAaaaaXY", "CAabbbXY", "CAaaabXY", "CAaabbXY", "CAababXY" and "CAabbaXY", where a and b are two different digits and X and Y are letters from the Latin alphabet subset { 'A', 'B', 'C', 'E', 'H', 'K', 'M', 'P', 'T', 'X' }. Your task is to write a program that calculates how many cars ca n be registered in Sofia for given magic weight. Input The input data should be read from the console. It will consist of a single value: the magic weight. The input data will always be valid and in the format described. There is no need to check it explicitly. Output The output should be printed on the console. It is a single value: the number of cars matching given magic value. Constraints • All input numbers will be integers in the range [1…1000]. • Allowed working time for your program: 0.25 seconds. • Allowed memory: 16 MB. Examples Input Output Matching Car Numbers 555 2 CA8999XX, CA9998XX 512 18 CA5999TX, CA5999XT, CA7799TX, CA7979TX, CA7997TX, CA7799XT, CA7979XT, CA7997XT, CA8888TX, CA8888XT, CA9995TX, CA9977TX, CA9797TX, CA9779TX, CA9995XT, CA9977XT, CA9797XT, CA9779XT 95 46 CA0555AC, CA0555BB, CA0005BC, CA0555CA, CA0005CB, CA1888AB, CA1888BA, CA1112BC, CA1112CB, CA2229AC, CA2229BB, CA2111BC, CA2229CA, CA2111CB, CA3444AC, CA3336AC, CA3444BB, CA3336BB, CA3444CA, CA3336CA, CA4777AB, CA4443AC, CA4777BA, CA4443BB, CA4443CA, CA5550AC, CA5550BB, CA5000BC, CA5550CA, CA5000CB, CA6667AB, CA6333AC, CA6667BA, CA6333BB, CA6333CA, CA7774AB, CA7666AB, CA7774BA, CA7666BA, CA8999AA, CA8881AB, CA8881BA, CA9998AA, CA9222AC, CA9222BB, CA9222CA

Problem 22. ** – Bit Flipper We are given a bit sequence in the form of 64-bit integer. We pass through the bits from left to right and we flip all sequences of 3 equal bits (111  000, 000  111). For example, 8773276988229695713 represents the bit sequence 0111100111000000111100001111000000011111100010100011100011100001. We flip from left to right all 3 consecutive equal bits: 0111100111000000111100001111000000011111100010100011100011100001  0000100000111111000111100001111111000000011110111100011100011101. The obtained 64-bit number after flipping is 594226797558351645. Your task is to write a program that enters a 64-bit integer, performs the above described flipping, and prints the obtained result as a 64-bit integer. Input The input data should be read from the console. It consists of a single 64-bit integer number. The input data will always be valid and in the format described. There is no need to check it explicitly. Output Print at the console the 64-bit integer, representing the obtained bits after the flipping. Constraints • The input number will be a 64-bit integer in the range [0 … 18 446 744 073 709 551 615]. • Allowed working time for your program: 0.1 seconds. • Allowed memory: 16 MB. Examples Input Output 8773276988229695713 594226797558351645 Explanation 8773276988229695713  0111100111000000111100001111000000011111100010100011100011100001  0000100000111111000111100001111111000000011110111100011100011101  594226797558351645

Input Output 594226797558350599 17222015390969265120 Explanation 594226797558350599  0000100000111111000111100001111111000000011110111100001100000111  1110111100000000111000111100000001111111000010000111101111100000  17222015390969265120