Homework 8 Due ( MT sections ) ( WTh sections ) at midnight Sun., 10/28 Mon., 10/29 Problems Reading is under week 7, however

Homework 8

• Due ( MT sections )

( WTh sections )

at midnightSun., 10/28

Mon., 10/29

• Problems

Reading is under week 7, however.

http://www.cs.hmc.edu/courses/2001/fall/cs5/week_08/homework.html

• Tutors availableSaturday afternoons Lac Lab (1-5)

Sunday afternoons Lac Lab and A/C (1-5)

Sunday evenings Lac Lab and A/C (7-10)

Monday evenings Lac Lab and A/C (8-12)

names and hours linked from the CS 5 home page

Problem 1

1 Display prices2 Compute average of prices3 Compute variance of prices4 Display index and value of lowest price5 Display index and value of highest price6 Your TTS investment strategy

9 Quit

Menu

What is it supposed to do ?

Initial Input Get the number of stock prices from the user

Get each stock price from the user into the array.

Create an array of the appropriate number of elements.

Problem 1

How do we do this ? Pseudocode...

Methods

public static void main(String[] args){ // first, create array stocks and fill it with values double[] stocks; // etc.

double total = sumArray(stocks);}

public static double sumArray(double[] arr){ double sum = 0.0; for (int i=0 ; i<arr.length ; ++i) { sum = sum + arr[i]; } return sum;}

7 Methods you will need:

public static void displayMenu()

public static void displayPrices(double[] arr)

double sumArray(double[] arr)

double averageArray(double[] arr)

double variance(double[] arr)

int indexOfSmallest(double[] arr)

int indexOfLargest(double[] arr)How do we know this ?

Method Notes

int indexOfSmallest(double[] arr)

double smallest(double[] arr)

Problem 2

0 1 2 3 4 5

0 1 2 3 4 5

0 1 2 3 4 5

A starting row of lights

2 is selected Each turn, a light is selected -- It and its neighbors switch states.

Goal: get all the lights off…

on off on off off on

Problem 20 1 2 3 4 5


Pseudocode// input the desired # of lights// create the array and fill randomly

// print the lights

// let the user select a light

// switch lights as appropriate

// check if the user has won…

What is a light ?

0 1 2 3 4 5

How should we represent these lights in Java ?


Lights Out -- Printing

// draw the current set of lights

|****| |****| | |****| |****| |****| | |****| |****| |****| | |****| |****| |****| | |****|

0 1 2 3 4 5 6 7

lights should be separated with vertical bars

OK to display all light numbers up to 15

print light numbers close to the center of each light

“off” lights should be 4x4 blocks of spaces

“on” lights should be 4x4 blocks of stars

0 1 2 3 4 5



|****| |****| | |****| |****| |****| | |****| |****| |****| | |****| |****| |****| | |****|

0 1 2 3 4 5

|****| |****| | |****| |****| |****| | |****| |****| |****| | |****| |****| |****| | |****|

0 1 2 3 4 5 6 7


// draw the current set of lightslights should be separated with vertical bars

OK to display all light numbers up to 15




0 1 2 3 4 5



|****| |****| | |****| |****| |****| | |****| |****| |****| | |****| |****| |****| | |****|

0 1 2 3 4 5

Lights Out -- Selecting

0 1 2 3 4 5

What lights are valid for the user to select?


Lights Out -- Switching

0 1 2 3 4 5

How do we switch the necessary lights on or off?


H.out.println(“Type the number of words: ”);int len = H.in.nextInt();

String[] quip; quip = new String[len];

for (int i=0 ; i<len ; ++i){ quip[i] = H.in.nextWord();}

for (int i=len-1 ; i>=0 ; --i){ H.out.print( quip[i] + “ ” );}

Arrays in pictures

int len

5





Arrays in pictures

int len

5

String[] quip





Arrays in pictures

int len

String[] quip

quip[0]quip[1]

quip[2] quip[4]quip[3]

5

array reference





Arrays in pictures

int len

String[] quip

quip[0]quip[1]


5

fall

leaves

after

leaves

fall

i is 0i is 1

i is 2i is 3

i is 4





Arrays in pictures

int len

String[] quip

quip[0]quip[1]


5

fall

leaves

after

leaves

fall

i is 4 i is 3 i is 2 i is 1 i is 0

fall leaves after leaves fall

This week in CS 5

• HW 8 (2 problems)M/T sections

W/Th sections

due Sunday, 10/28 at midnight

due Monday, 10/29 at midnight

Recitation for HW8 will be Friday 10/26

• Getting data together -- arrays !

No recitation this Friday, 10/19

Reading: Week 7’s online notes

• Indenting will count on HW 8 (and after)!See HW for notes on

aligning things correctly, as well as deleting files.

public static int numSyllables(String w){ int numSyls = 0; int len = w.length();

if ( isVowel(w.charAt(0)) ) // an initial vowel ? ++numSyls;

for (int i=1 ; i<w.length() ; ++i) { // vowel preceded by a consonant if ( isVowel(w.charAt(i))&& !isVowel(w.charAt(i-1)) ) ++numSyls; } // final ‘e’ preceded by a consonant if ( w.charAt(len-1) == 'e’ && len >= 2 && !isVowel(w.charAt(len-2)) ) --numSyls;

if (numSyls < 1) // every word has at least 1 syllable numSyls = 1;

return numSyls;}

Syllable counting

Take in a number of words and print them out in reverse order. (To be specific, suppose it’s 5 words.)

A puzzle...


A puzzle...

String s1 = H.in.nextWord();String s2 = H.in.nextWord();String s3 = H.in.nextWord();String s4 = H.in.nextWord();String s5 = H.in.nextWord();

H.out.print( s5 + “ ” );H.out.print( s4 + “ ” );H.out.print( s3 + “ ” );H.out.print( s2 + “ ” );H.out.print( s1 + “\n” );

Not a very flexible solution...

Arrays - lists of data items

String[] quip;

quip = new String[5];

for (int i=0 ; i<5 ; ++i){ quip[i] = H.in.nextWord();}

declares a String array named quip

declares five Strings named quip[0]…quip[4]

loop through the array

index

Arrays in code


String[] quip; // create an empty arrayquip = new String[len]; // create array elements

for (int i=0 ; i<len ; ++i){ quip[i] = H.in.nextWord(); // input each element}

// now print them out in reverse order…

Sentence palindromes

bores are people that say that people are bores

fall leaves after leaves fall

you can cage a swallow, can’t you, but you can’t swallow a cage, can you?

First Ladies rule the state and state the rule, “Ladies First!”

Strings

Be careful not to go out of bounds!

Element typesdouble, int, String,boolean, char, (any type) … char

The ith element

Example Declaration

Length

arr[i] s.charAt(i)

double[] arr;arr = new double[100];

String s;

java.lang.StringIndexOutOfBoundsException: -1

java.lang.ArrayIndexOutOfBoundsException: -1

arr.length s.length()

Warning

Range from 0 up to length-1

vsArrays

T. T. Securities

Input stock prices for a number of days in a row, and then analyze that data… .

1 Display prices2 Compute average of prices3 Compute standard deviation of prices4 Display index and value of lowest price5 Display index and value of highest price6 Your TTS investment strategy

9 Quit

Which choice would you like?

Menu:

Arrays and Methods

public static double sumArray(double[] arr)

Using sumArray

public static void main(String[] args){ // prompt for and input nStocks double[] stocks = new double[nStocks]; // input and assign each stocks[i] double stockSum = sumArray(stocks); H.out.println(“The sum is ” + stockSum);}

public static double sumArray(double[] arr){ // see previous page … return sum;}

double[] stocks

90.0 10.0 60.0 42.0 75.0 70.0

double[] arr

Using sumArray



double[] stocks

90.0 10.0 60.0 42.0 75.0 70.0

double[] arr

2 references referring to the same list of data

Array Searching

public static double findMax(double[] arr)

T. T. Securities

Find the most profitable strategy for buying and selling the stock among the prices in the array...

Day 0 Price is 90.0Day 1 Price is 10.0Day 2 Price is 60.0Day 3 Price is 42.0Day 4 Price is 75.0Day 5 Price is 70.0

Lights Out !

0 1 2 3 4 5

0 1 2 3 4 5

0 1 2 3 4 5

A starting row of lights

2 is selected Each turn, a light is selected -- It and its neighbors switch states.

Goal: get all the lights off…

on on off off off on

Lights Out !

Features of the game:

// allow the user to set the // number of lights from 3 to 15

// start each light randomly on or off


// allow the user to select a light// only allow valid lights !

// update the set of lights and repeat

Lights Out !


0 1 2 3 4 5

| |****|****|****| |****| | |****|****|****| |****| | |****|****|****| |****| | |****|****|****| |****|

0 1 2 3 4 5 6 7

lights should be separated with vertical bars

may display all light numbers up to 15




Lights Out !

// allow the user to select a light

// only allow valid lights !

Summary

double[] stocks;String[] quip;int[] grades;

To declare an array:

To loop through an array:

stocks = new double[nStocks];quip = new String[nWords];grades = new int[42];

for (int i=0 ; i<stocks.length ; ++i){ do something with stocks[i] in here ...}

To declare an array’s individual elements:

(x[i] - xav)2

Ni

0 1 2 3 4 5

0 1 2 3 4 5

0 1 2 3 4 5

Drawing room

Printed version following this slide

This week in CS 5

• HW 8 (2 problems)M/T sections

W/Th sections

due Sunday, 10/28 at midnight

due Monday, 10/29 at midnight

Recitation for HW8 will be Friday 10/26

• Putting data together with arrays

No recitation this Friday, 10/19

-- Reading: Week 7’s online notes

• Indenting will count on HW 8 (and after)!See HW for notes on

aligning things correctly, as well as deleting files.

if ( isVowel(w.charAt(0)) ){ ++numSyls;}


String[] quip;



String[] quip

String[] quip

quip[0]quip[1]


fall

leaves

after

leaves

fall

- declares a String array named quip

- declares five Strings named quip[0]…quip[4]

- looping through the array

Arrays in code


String[] quip; // create array variablequip = new String[len]; // create data variables

for (int i=0 ; i<len ; ++i){ quip[i] = H.in.nextWord(); // input each word}







Arrays in pictures

int len

String[] quip

quip[0]quip[1]


5

fall

leaves

after

leaves

fall

Arrays vs. Strings



The ith element

Example Declaration

Length

arr[i] s.charAt(i)


String s;




Warnings


T. T. Securities

Input stock prices for a number of days in a row, and then analyze that data… .

1 Display prices2 Compute average of prices3 Compute standard deviation of prices4 Display index and value of lowest price5 Display index and value of highest price6 Your TTS investment strategy

9 Quit

Which choice would you like?

Menu:

Arrays and Methods

public static double sumArray(double[] arr)

Using sumArray



double[] stocks

90.0 10.0 60.0 42.0 75.0 70.0

double[] arr

stocks[0] stocks[1] stocks[2] stocks[3] stocks[4] stocks[5]

Array Searching

public static double findMax(double[] arr)

T. T. Securities



Lights Out !

Features of the game:

// allow the user to set the // number of lights from 3 to 15

// start each light randomly on or off


// allow the user to select a light// only allow valid lights !

// update the set of lights and repeat

Summary

double[] stocks;String[] quip;int[] grades;

To declare an array:

To loop through an array:

stocks = new double[nStocks];quip = new String[nWords];grades = new int[42];

for (int i=0 ; i<stocks.length ; ++i){ do something with stocks[i] in here ...}

To declare an array’s individual elements:


A puzzle...

String s1 = H.in.nextWord();String s2 = H.in.nextWord();String s3 = H.in.nextWord();String s4 = H.in.nextWord();String s5 = H.in.nextWord();

H.out.print( s1 + “ ” );H.out.print( s2 + “ ” );H.out.print( s3 + “ ” );H.out.print( s4 + “ ” );H.out.print( s5 + “\n” );

Not a very flexible solution...


String[] quip;



declares a String array named quip

declares five Strings named quip[0]…quip[4]

loop through the array

index

Arrays in code


String[] quip; // create an empty arrayquip = new String[len]; // create array elements

for (int i=0 ; i<len ; ++i){ quip[i] = H.in.nextWord(); // input each element}



Strings



The ith element

Example Declaration

Length

arr[i] s.charAt(i)


String s;




Warning


vsArrays

Day 0 Price is 95.0Day 1 Price is 15.0Day 2 Price is 90.0Day 3 Price is 10.0Day 4 Price is 60.0Day 5 Price is 42.0Day 6 Price is 75.0Day 7 Price is 70.0

It’s not always with the minimum or maximum !

Methods

displayMenu displayPrices

sumArrayaverageArraystdDevArray

indexOfSmallestindexOfLargest

T. T. Securities



Using sumArray



double[] stocks

90.0 10.0 60.0 42.0 75.0 70.0

double[] arr

Documents

Homework 8 Due ( MT sections ) ( WTh sections ) at midnight Sun., 10/28 Mon., 10/29 Problems Reading is under week 7, however