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Lynbrook Computer Science

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Lynbrook Computer Science

Member Meeting: October 27th, 2008

- Two Divisions:
- Intermediate
- Senior

- First Competition: December 19th, 2008
- Short Problem (like CAML) + Programming problem
- Topics:
- Boolean Logic
- Graph Theory
- Recursion
- Converting between Number Systems (dec, oct, hex, bin)
- Data Structures

BASIC Program:

If the following program prints 15, what was the input?

1input N

2if N > 5 then N = N + 8

3if N > 12 then N = N - 6

4if N >= 8 then N = N + 1

5print N

6end

Work Backwards:

- Line 4: N = 14
- Line 3: N = 20
- Line 2: N = 12
Answer: 12

Computer Number Systems

- What is the base 16 value of FEDCBA16 – ABCDEF16?
Recursive Functions

- Find f(10, 5) given the following:
- If x > y then f(x, y) = f(x-2, y+1) + 3
- If x < y then f(x, y) = f(x+1, y-3) + 2
- Otherwise, f(x, y) = 5

- Work from right to left, and borrow as needed:
1A – F = B

1B – E – 1 = C

1C – D – 1 = E

D – C – 1 = 0

E – B = 3

F – A = 5

Answer: 530ECB16

Work through the recursion

- f(10, 5) = f(8, 6) + 3
- f(8, 6) = f(6, 7) + 3
- f(6, 7) = f(7, 4) + 2
- f(7, 4) = f(5, 5) + 3
- F(5, 5) = 5
Going backwards and summing up everything,

Answer = 16

- More sample problems available at ACSL.org
- TopCoder competitions:
- Single Round Match (SRM): 10/28 @ 6PM
- TopCoder High School SRM: 10/28 @ 6PM
- Register before 3PM!

- Marathon Match : 10/29-11/5

- Remember to sign in!
- Turn in your checks ($15, payable to Lynbrook ASB) into Stephen Li if you haven’t already!
- Check for updates at LynbrookCS.com