Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Algorithm 1: The...
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Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal . . . Math 130 Intro to Computer Programming Algorithms Lecture # 01 01/21/05 B Smith: Required 45 to 50 minutes. Stirred up few questions. Needs to be more interactive and less general/abast ract. Score 3 with improv, 2.5 if used as is. B Smith: Great for independent study; not so great otherwise. B Smith: Not used Fall05. Not needed; not helpful
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Transcript of Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Algorithm 1: The...
Algorithm 1: The Morning RoutineGet out of bedShowerBathe kidsPrepare cereal...
Algorithm 1: The Morning RoutineGet out of bedShowerBathe kidsPrepare cereal...
Math 130 Intro to Computer Programming
AlgorithmsLecture # 01
01/21/05
Math 130 Intro to Computer Programming
AlgorithmsLecture # 01
01/21/05
B Smith:
Required 45 to 50 minutes. Stirred up few questions. Needs to be more interactive and less general/abastract. Score 3 with improv, 2.5 if used as is.
B Smith:
Required 45 to 50 minutes. Stirred up few questions. Needs to be more interactive and less general/abastract. Score 3 with improv, 2.5 if used as is.
B Smith:
Great for independent study; not so great otherwise.
B Smith:
Great for independent study; not so great otherwise.
B Smith:
Not used Fall05. Not needed; not helpful
B Smith:
Not used Fall05. Not needed; not helpful
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Overview
• Solving problems– mysterious or methodical– luck or by design
• Algorithms– recipes
• Values and variables– quantity and place holders
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How do we solve problems?
• Largely empirical– “Doing heart surgery in this manner works”
• History– “This is how Alice did it…”
• Inspiration– “I don’t know how, but I solved it!”
• Brute force– Trial-and-error
• The scientific method
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0100111010110010101010101001010101010100110010101010101001011010011101010101010010010111010011110101010111110101010001101…
sterilize(saw,alcohol);raise_hammer();lower_hammer(fast);start(saw);/* etc. etc. */
Patient has elevated pressure in anterior parietal lobe
The Problem-solving Process
Problem
specification
Algorithm
Program
Executable (solution)
Design
Implementation
Compilation
"Doctor, my head hurts"
Analysis
1. Sterilize cranial saw2. Anaesthetize patient3. Remove top of skull4. Get the big spoon...5. etc., etc.
B Smith:
Use math as a useful application. How about finding the roots of 2x^2+3x-4 = 0? What would be the algorithm.
B Smith:
Use math as a useful application. How about finding the roots of 2x^2+3x-4 = 0? What would be the algorithm.
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The Problem-solving Process
Problem specification
Algorithm
Program
Executable (solution)
Analysis
Design
Implementation
Compilation
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• A sequence of instructions specifying the steps required to accomplish some task
• Named after:– Muhammad ibn Mūsā al-
Khwārizmi– Circa 780-850 C.E. (Common Era)
http://jeff560.tripod.com/khowar.jpg
Algorithm
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Algorithm –History
Muhammad ibn Musa al-Khwarizmihttp://www-gap.dcs.st-andrews.ac.uk/~history/Mathematicians/Al-Khwarizmi.html
• Book on arithmetic:– Hindu numeration, decimal numbers, use of
zero, method for finding square root– Latin translation (c.1120 CE): “Algoritmi de
numero Indorum”
• Book on algebra– “Kitāb al-jabr wa’l-muqābala”
• (“Rules of restoring and equating”)
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• A sequence of instructions describing how to do a task
Algorithm – Working Definition
As opposed to actually executing the instructions!
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sterilize(saw,alcohol);raise_hammer();lower_hammer(fast);start(saw);/* etc. etc. */
The Problem-solving Process
Problem specification
Algorithm
Program
Executable (solution)
Analysis
Design
Implementation
Compilation
"Doctor, my head hurts"
Patient has elevated pressure in anterior parietal lobe.
1. Sterilize cranial saw2. Anaesthetize patient3. Remove top of skull4. Get the big spoon...5. etc., etc.
010011101011001010101010100101010101010011001010101010100101101001110101010101001001011101001111010101011111010101000110100001101...
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Algorithm -- Examples
• A cooking recipe• Assembly instructions for a model car,
boat, etc.• The rules of how to play a game• VCR instructions• Description of a martial arts technique• Directions for driving from A to B• A knitting pattern• A car repair manual
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Algorithm – Examples (cont)
• Recipe for Almond and honey slice• Recipe for Arroz con pollo
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Almond and Honey Slice
1/2 quantity Shortcrust Pastry
185 g unsalted butter100 g castor sugar5 tablespoons honey50 ml cream50 ml brandy or any
other liqueur or spirit300 g flaked almonds
Preheat oven for 200° CLine a 30 cm 20 cm
baking tray with baking paper, and then with pastry
Bake blind for 20 minutes, then remove weights and foil
Turn oven up to 220° C.Bring remaining ingredients
to a boil, stirring.Spread evenly over pastry.Bake until topping is
bubbling and has caramelized evenly, about 15 minutes.
Cool before cutting into fingers or squares.
From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.
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Almond and Honey Slice
1/2 quantity Shortcrust Pastry
185 g unsalted butter100 g castor sugar5 tablespoons honey50 ml cream50 ml brandy or any
other liqueur or spirit300 g flaked almonds
Preheat oven for 200° CLine a 30 cm 20 cm
baking tray with baking paper, and then with pastry
Bake blind for 20 minutes, then remove weights and foil
Turn oven up to 220° C.Bring remaining ingredients
to a boil, stirring.Spread evenly over pastry.Bake until topping is
bubbling and has caramelized evenly, about 15 minutes.
Cool before cutting into fingers or squares.
From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.
Instructions are given in the order in which they are performed (“executed”)
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Correct Algorithm?Cut chicken into pieces
and brown the pieces on all sides in a casserole dish in hot olive oil.
Remove the chicken; to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden.
Add bay leaf, whole tomatoes, and chicken broth.
When the broth boils add salt, saffron and rice.
Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender.
Add beans and artichokes during last 10 minutes of cooking.
From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, 1968.
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Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.
Remove the chicken and to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden.
Add bay leaf, whole tomatoes, and chicken broth.
When the broth boils add salt, saffron and rice.
Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender.
Add beans and artichokes during last 10 minutes of cooking.
From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, 1968.
Correct Algorithm?
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Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.
Remove the chicken and to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden.
Add bay leaf, whole tomatoes, and chicken broth.
When the broth boils add salt, saffron and rice.
Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 10 minutes.
Add beans and artichokes.
Cover, and bake for another 10 minutes or until rice is tender.
Correct Algorithm?
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From Algorithms to Programs
Problem
C ProgramC Program
AlgorithmAlgorithm: A sequence of instructions describing how to do a task (or process)
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Components of an Algorithm
• Variables and values• Instructions• Sequences• Procedures• Selections• Repetitions• Documentation
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Values
• Represent quantities, amounts, rates, etc.• May be numerical, alphabetical or even
other items• A related unit may or may not be specified
– Add 3 cups of flour – Pull rip-cord
• Example:– Recipe ingredients (how big, how hot, how long)
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Almond and Honey Slice
1/2 quantity Shortcrust Pastry
185 g unsalted butter100 g castor sugar5 tablespoons honey50 ml cream50 ml brandy or any
other liqueur or spirit300 g flaked almonds
Preheat oven for 200° CLine a 30 cm 20 cm
baking tray with baking paper, and then with pastry
Bake blind for 20 minutes, then remove weights and foil
Turn oven up to 220° C.Bring remaining ingredients
to a boil, stirring.Spread evenly over pastry.Bake until topping is
bubbling and has caramelised evenly, about 15 minutes.
Cool before cutting into fingers or squares.
From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.
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Almond and Honey Slice
1/2 quantity Shotcrust Pastry
185 g unsalted butter100 g castor sugar5 tablespoons honey50 ml cream50 ml brandy or any
other liqueur or spirit300 g flaked almonds
Preheat oven for 200° CLine a 30 cm 20 cm
baking tray with baking paper, and then with pastry
Bake blind for 20 minutes, then remove weights and foil
Turn oven up to 220° C.Bring remaining ingredients
to a boil, stirring.Spread evenly over pastry.Bake until topping is
bubbling and has caramelised evenly, about 15 minutes.
Cool before cutting into fingers or squares.
From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.
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Variables
This jarcan contain
10 cookies
50 grams of sugar
3 slices of cake
etc.
ValuesVariable
• Are containers for values – places to store values
• Example:
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Restrictions on Variables
• Variables may be restricted to contain a specific type of value
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Components of an Algorithm
Values and Variables• Instruction (a.k.a. primitive)• Sequence (of instructions)• Procedure (involving instructions) • Selection (between instructions)• Repetition (of instructions)• Documentation (beside instructions)
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Instructions (Primitives)
• Some action that is simple......and unambiguous......that the system knows about......and should be able to actually do
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Instructions – Examples
• Take off your shoes• Count to 10 • Cut along dotted line• Knit 1• Purl 2• Firmly Pull rip-cord • Sift 10 grams of sulfur
Directions to perform specific actions on values and variables.
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Instructions -- Application• Some instructions can only be
applied to specific types of values or variables
• Examples:
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Instructions (Primitives) -- Recommendations
• When writing an algorithm, make each instruction simple and unambiguous
• Example:
Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.
Cut chicken into pieces.Heat olive oil in a casserole dish.Brown the chicken pieces in the casserole dish.
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Instruction (Primitives)
• When writing an algorithm, make the instructions simple and unambiguous.
• Example:
Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.
Cut chicken into pieces.Heat olive oil in a casserole dish.Brown the chicken pieces in the casserole dish.
A “sequence” of simple instructions
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Summary
• Problem Solving Process• Algorithms• Components of Algorithms
– Values and Variables– Instructions– to be continued...
Reading
Bronson, Ch 1 and Ch 2
