Scrum Gathering 2012 Shanghai_工程实践与技术卓越分会场：编程练习(尹哲)

Programming
Exercises

12年6月5日星期二

Who am I?

尹哲：terry@odd-e.com twitter: terryyin weibo: terry尹哲 2


Why Programming Exercises?

4


Question

Does software company need to
train programmers?

6


Leonhard Euler Dojo

vs.

7


What is ProjectEuler.net?

8


ProjectEuler.net
"Project Euler exists to encourage, challenge, and develop the skills and enjoyment of anyone with
an interest in the fascinating world of mathematics."

• Project Euler is a series of challenging mathematical/computer
programming problems that requires more than just mathematical
insights to solve.

9


ProjectEuler.net

10


ProjectEuler.net

11


Expectations

Mathematics
So lution implementing
Hig h perfor mance co d ing

So lving problem
ind ivi dually

12


Example: Quick & Dirty

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?

13


Another Example

14


int i, j, k, n, sum;
int factorial[10000];

int* getfactorial(int n)
{
factorial[0] = 1;
k = 0;
for(i = 2; i <= n; i++)
{
• It’s too simple for for(j = 0; j <= k; j++)
factorial[j] *= i;
Java, Ruby or Python, for(j = 0; j <= k; j++)
for which they can {
if(factorial[j] >= 10)
handle big numbers by {
factorial[j+1] += (factorial[j] - (factorial[j] % 10)) / 10;
default. factorial[j] = factorial[j] % 10;

• So let’s look at C/C++. if(j == k)
k++;

• Real code copied from }
}

the forum. }
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;
} 15


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

17


#include<iostream>

using namespace std;

int i, j, k, n, sum;
int factorial[10000];
Why the big number is named ‘factorial’
int* getfactorial(int n)
{ in my previous implementation?
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++)
Where’s the code for big number?
{
if(factorial[j] >= 10)
{
factorial[j+1] += (factorial[j] - (factorial[j] % 10)) / 10;
factorial[j] = factorial[j] % 10;
if(j == k)
k++;
}
}
}
return factorial;
}
18


#include <stdio.h>

#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;
OK, too hard to reuse. It’s not bigNum2[0] = 1;
counter = 2;
that hard to invent the wheel again. 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]++;
Design? }
}

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);
} 19


ing exercises
Problem so lv
tant skills
✓ Train ver y impor
w
as inter vie
✓Often use d
ques tions
i n skills in
✓ Probab ly also tra
n able co de,
maki ng maintai
a little.

•Don’t do it before bed time... 20


What is Cyber Dojo?

21


RED - GREEN - REFACTOR

25


Which One Do You Prefer?

29


Poker Hands

30


Poker Hands Kata

31


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

32


Example: Complicated
Transaction

33


Why Did I Do It Right
With Only One Try?

34


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){
}
TEST(poker_hand, compare_high_cards_3nd_4th_5th){
}
TEST(poker_hand, compare_high_card_and_one_pair){
}
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"));
}

...

35


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

36


Discuss

Training
in workshop

Develop
in concurrence

Deliver
for acceptance

37


Odd-e
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• One week course simulating how it feels to be on a Scrum project
- Realistic exercise to work on as a team
- Topics covered: A-TDD, Build Automation, Sprint Planning, Pair
Programming, Continuous Integration, Test-Driven Development,
Working in teams, Collective Code Ownership, Mocking, Code
Smells & Refactoring, Good unit tests,Emergent Design, Working
with Legacy Code, Craftsmanship
- Maximum 10 people, in Odd-e office
- Java and C++ version
- Fulfills the ScurmAlliance CSD

More info at:
http://www.odd-e.com/courses.php?id=201205SingaporeCSD 38


Coaching

39


Scrum Gathering 2012 Shanghai_工程实践与技术卓越分会场：编程练习(尹哲)

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