Programming Exercises - Terry Yin - Agile SG 2013

Presented in Agile Singapore 2013 Conference

Programming skills are so fundamental these days that people seem to take them for granted. However, a 10 year veteran might only have accumulated 1 year of experience as performing the same programming tasks over 10 years would not have resulted in 10 years' worth of skill development. To improve ones programming skills requires deliberate and intentional practice. This session will introduce a couple of ways to do programming exercises and will demonstrate the difference in their effectiveness. Terry will start you off on the journey to mastering the craft of programming.

Transcript

1. Programming
   Exercises
   Terry Yin
   

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2. Who am I?
   2
   

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3. Why Programming Exercises?
   3
   

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5. Quality vs. Quantity
   5
   

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6. Gamification
   6
   

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7. Does software company need to
   train programmers?
   7
   Question
   

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8. 8
   vs.
   Leonhard Euler Dojo
   

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9. What is ProjectEuler.net?
   9
   

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10. ProjectEuler.net
    • Project Euler is a series of challenging mathematical/computer
    programming problems that requires more than just mathematical
    insights to solve.
    10
    "Project Euler exists to encourage, challenge, and develop the skills and enjoyment of anyone with
    an interest in the fascinating world of mathematics."
    

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11. 11
    ProjectEuler.net
    

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12. 12
    ProjectEuler.net
    

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13. Expectations
    13
    Mathematics
    Solution implementing
    High performance coding
    Solving problem
    individually
    

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14. Example: Quick & Dirty
    14
    Once you solved a problem, you are entitled to join the forum for this problem. You can
    share your solution with the other people who have also solved it. And the post usually
    start with this sentence:
    
    Good coding habit?
    

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15. Another Example
    15
    

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16. • It’s too simple for
    Java, Ruby or Python,
    for which they can
    handle big numbers by
    default."
    • So let’s look at C/C++."
    • Real code copied from
    the forum.
    16
    int i, j, k, n, sum;!
    int factorial[10000];!
    "
    int* getfactorial(int n)!
    {!
    factorial[0] = 1;!
    k = 0;!
    for(i = 2; i <= n; i++)!
    {!
    for(j = 0; j <= k; j++)!
    factorial[j] *= i;!
    for(j = 0; j <= k; j++)!
    {!
    if(factorial[j] >= 10)!
    {!
    factorial[j+1] += (factorial[j] - (factorial[j] % 10)) / 10;!
    factorial[j] = factorial[j] % 10;!
    if(j == k)!
    k++;!
    }!
    }!
    }!
    return factorial;!
    }!
    "
    int getsum(int* array, int k)!
    {!
    sum = 0;!
    for(i = 0; i <= k; i++)!
    sum += array[i];!
    return sum;!
    }!
    "
    int main()!
    {!
    int* factorial = getfactorial(n);!
    sum = getsum(factorial, k);!
    cout << "\nThe sum of the digits of " << n << "! is " << sum << ".\n";!
    return 0;!
    }!
    

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18. 18
    Big number again. Ha ha, I did that
    before! Let me reuse it...
    

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19. #include!
    "
    using namespace std;!
    "
    int i, j, k, n, sum;!
    int factorial[10000];!
    "
    int* getfactorial(int n)!
    {!
    factorial[0] = 1;!
    k = 0;!
    for(i = 2; i <= n; i++)!
    {!
    for(j = 0; j <= k; j++)!
    factorial[j] *= i;!
    for(j = 0; j <= k; j++)!
    {!
    if(factorial[j] >= 10)!
    {!
    factorial[j+1] += (factorial[j] - (factorial[j] % 10)) / 10;!
    factorial[j] = factorial[j] % 10;!
    if(j == k)!
    k++;!
    }!
    }!
    }!
    return factorial;!
    }
    19
    Why the big number is named ‘factorial’
    in my previous implementation?
    Where’s the code for big number?
    

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20. 20
    #include
    "
    #define NUMB 120 // 9 * 120 = 1080 total digits.
    #define SIZE 1000000000 // 9 digit numbers
    "
    int main() {
    int i = 0;
    int j = 0;
    int bigNum1[NUMB];
    int bigNum2[NUMB];
    int bigNum3[NUMB];
    int counter = 0;
    "
    for (i = 0; i < NUMB; i++) {
    bigNum1 = 0;
    bigNum2 = 0;
    bigNum3 = 0;
    }
    "
    bigNum1[0] = 1;
    bigNum2[0] = 1;
    counter = 2;
    i = 0;
    "
    while (i == 0) {
    counter++;
    for (j = 0; j < NUMB; j++) {
    bigNum3[j] = bigNum2[j] + bigNum1[j];
    }
    for (j = 0; j < NUMB-1; j++) {
    while (bigNum3[j] >= SIZE) {
    bigNum3[j] -= SIZE;
    bigNum3[j+1]++;
    }
    }
    if (bigNum3[111] >= 1)
    break;
    for (j = 0; j < NUMB; j++) {
    bigNum1[j] = bigNum2[j];
    bigNum2[j] = bigNum3[j];
    }
    }
    "
    printf("\n");
    printf("P025 answer = %u", counter);
    }
    OK, too hard to reuse. It’s not
    that hard to invent the wheel again.
    

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21. 21
    Problem solving exercises
    ✓Train very important skills
    ✓Often used as interview
    questions
    ✓Probably also train skills in
    making maintainable code,
    a little.
    •Don’t do it before bed time...
    

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22. What is Cyber Dojo?
    22
    

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26. RED - GREEN - REFACTOR
    26
    

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27. 27
    Unit Test
    Integration Test
    Functional Test
    

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31. Refactoring Dojo
    31
    

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32. Code Retreat
    ✓-G[DQCTFQPN[
    ✓7UGCRNCKPVGZVGFKVQT
    ✓4GCNN[UOCNNOGVJQFU
    ✓0QEQPFKVKQPU
    ✓0QNQQRU
    ✓0QRTKOKVKXGV[RGUQPKPVGTHCEG
    ✓0QTGVWTPXCNWGU
    32
    A day-long practice-intensive event for programmers,
    
    popularized by Corey Haines.
    

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33. Which One Do You Prefer?
    33
    

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34. Poker Hands
    34
    

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35. Poker Hands Kata
    35
    

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36. Poker Hands in ProjectEuler
    •This is not a very hard problem to solve,
    comparing to most of the problems listed in
    ProjectEuler.net"
    •But it’s hard to solve it without bugs if you don’t
    have unit tests."
    •Problem 54 in projectEuler.net
    36
    

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37. Example: Complicated
    Transaction
    37
    

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38. Why Did I Do It Right
    With Only One Try?
    38
    

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39. 39
    TEST(poker_hand, comparing){
    CHECK(pokerHand("4H 5C 6S 7S TD")< pokerHand("2C 3S 7S 8D KD"));
    CHECK(!(pokerHand("4H 5C 6S 7S KD")< pokerHand("2C 3S 7S 8D TD")));
    CHECK(pokerHand("4H 5C 6S 7S KD")> pokerHand("2C 3S 7S 8D TD"));
    }
    TEST(poker_hand, compare_cards){
    CHECK(pokerHand("3H 5C 6S 7S 8D")< pokerHand("4H 5C 6S 7S 9D"));
    CHECK(pokerHand("3H 5C 6S 7S 9D")< pokerHand("4H 5C 6S 7S TD"));
    CHECK(pokerHand("3H 5C 6S 7S TD")< pokerHand("4H 5C 6S 7S JD"));
    CHECK(pokerHand("3H 5C 6S 7S JD")< pokerHand("4H 5C 6S 7S QD"));
    CHECK(pokerHand("3H 5C 6S 7S QD")< pokerHand("4H 5C 6S 7S KD"));
    CHECK(pokerHand("3H 5C 6S 7S KD")< pokerHand("4H 5C 6S 7S AD"));
    }
    TEST(poker_hand, compare_high_cards_2nd){
    CHECK(pokerHand("3H 5C 6S 7S 9D")< pokerHand("3H 5C 6S 8S 9D"));
    }
    TEST(poker_hand, compare_high_cards_3nd_4th_5th){
    CHECK(pokerHand("3H 5C 6S 8S 9D")< pokerHand("3H 5C 7S 8S 9D"));
    CHECK(pokerHand("3H 4C 7S 8S 9D")< pokerHand("3H 5C 7S 8S 9D"));
    CHECK(pokerHand("2H 5C 7S 8S 9D")< pokerHand("3H 5C 7S 8S 9D"));
    }
    TEST(poker_hand, compare_high_card_and_one_pair){
    CHECK(pokerHand("3H 5C 6S 8S 9D")< pokerHand("3H 5C 7S 8S 8D"));
    }
    TEST(poker_hand, compare_one_pairs){
    CHECK(pokerHand("3H 5C 6S 9S 9D")> pokerHand("3H 5C 7S 8S 8D"));
    CHECK(pokerHand("5C 6S 9S 9D KD")> pokerHand("5C 7S 8S 8D AD"));
    CHECK(pokerHand("5C 6S 9S 9D KD")< pokerHand("5C 7S 9S 9D AD"));
    }
    "
    ...
    

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40. Do deliberate exercises.
    Alone and with the others.
    Always use good practices.
    Have fun.
    40
    

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