Arrays

One-Dimensionalinitialize & display

Arrays as Arguments

Two-dimensional initialize & display

Part I

Data Types

a simple or atomic

a structured

* *

char, int, float, double

array, struct, union, class

Structured Data Type - Array

An array is a collection of data storage locations, each of which holds the same type of data. Each storage location is called an element of the array.

Each element is referred to as an indexed or subscripted variable.

Array Declaration

SyntaxdataType arrayName [[ ConstIntExpression ]]

The number of elements in an array is stated within square brackets, [ ][ ].

Examplesdouble angle [4]; constant POLY = 8;int testScore [12]; double angle [POLY]; char password [8];

Array Storage

Each array has sufficient memory reserved to hold the number of data items of the given type.

Initializing an array sets up the address of the first element. Addresses of all other elements are offsets from the starting address.

Array Element Access

Syntax

arrayName [ indexExpression ]

Program access to each of the array elements is by referring to an offset from the array name. Array elements are counted beginning with zero.

Array Element Access

double angle[4]; // declaration

Exampleangle [0] = 6.21;angle [1] = 15.89;angle [2] = 7.5;angle [3] = -45.7;

angle sub zero = 6.21angle sub one = 15.89angle sub two = 7.5angle sub three = -45.7

* * *

Using Array Elements

a write the contents of an array element:cout << angle[2];

a assign values to an array element:cin >> angle[3];angle[6] = pow(axis,4);

a use it as a parameter:y = sqrt(angle[0]);

a use it in an expression:x = 2.5 * angle[1] + 64;

* * * *

Array Component Access

for(indexindex=0; index index < arraySize; indexindex++)myArray[indexindex] = 0.0;

100

* *

Zero out an entire array. (Initialize every element to 0.0.)

Off Set

memoryaddresses

starting address

off set by one unit

off set by two units

off set by three units

[ 0 ]

[ 1 ]

[ 2 ]

[ 3]

@#$

@#$

Out-of-Bounds Array Index

memoryaddresses

angle[4] = 135;

cout << angle[5];

[ 0 ]

[ 1 ]

[ 2 ]

[ 3]

@#$

@#$

Declare an Array

Syntaxtype arrayName[index];

Exampledouble dailyHigh[23] ;

int quizGrade[132] ;

char ASURiteID[5] ;

*

Initialize an Array Element

SyntaxarrayName[index] = value;

ExampledailyHigh[18] = 16.7;

quizGrade[2] = 15;

ASURiteID[3] = ‘d’;

*

Initialize an Array

double angle[4] = {16.21, 15.89, 7.5, -45.7};

double ATtoCG[5] = {.64, .89, .76, .83, .65};

int scores[12] = {210, 198, 203, 188, 200, 224, 220, 217, 211, 194, 197, 189};

double iona[8] = {0.0};*

Initialize an Array

int scores[ ] = {210, 198, 203, 188, 200, 224, 220, 217, 211, 194, 197, 189};

char name[4] = {‘Z’, ‘o’, ‘l’, ‘a’};

char name[4] = “Zola”; // no braces or ,char phrase [ ] = “Hello World”;

* *

Initialize an Array

double angle[4]; // declaration

Exampleangle [0] = 6.21;angle [1] = 15.89;angle [2] = 7.5;angle [3] = -45.7;

angle sub zero = 6.21angle sub one = 15.89angle sub two = 7.5angle sub three = -45.7

*

Sequencing Through an Array

Use the for statement to sequence through an array.

Total the contents of an array:sum = 0;for(index=0; index < 7; index++)

sum = sum + grades[index];

Loading an Array

double grade[10];

int index;

for(index=0; index < 10; index++){

cout<<“Enter a grade “;

cin >> grade[index];

}

Finding the Max/Min Value

Set the max or min to element zero.

Use a for loop to cycle through the array.

Compare each element to the max/min.

If necessary, assign a new value to max/min.

How would you do this?

*

Finding the Maximum Value

double find_max(int temp[30]){

max = temp[0];

for(index=0; index < 30; index++)if (temp[index] > max)

max = temp[index];return (max);

}*

Finding the Minimum Value

double find_min(int temp[30]){

min = temp[0];

for(index = 1; index < 30; index++)if (temp[index] << min)

min = temp[index];return ( min );

}

*

Aggregate Assignment - NOT!

There are no aggregate assignments with arrays. That is, you may not assign one array to another.

int x[5] = {11, 22, 33, 44, 55};

int y[5];

y = x; y[ ] = x[ ];

Arrays as Arguments

void find_max(int temp[ ]temp[ ]){

max = temp[0];

for(index = 1; index < 30; index++)if (temp[index] > max)

max = temp[index];

}

double find_max(int temp[ ]temp[ ])

*

return max;

Passing an Array/Element

find_max(temptemp); // no [ ]

inventory(priceprice, quantityquantity, amountamount); // 3 arrays

words(cupletcuplet);

find_max(temp[3]temp[3]);

inventory(priceprice, quantity[4]quantity[4], amount[12]amount[12]);

words(cupletcuplet);

*

Passing an Array

formal parameterformal parameter formal parameterformal parameterdeclaration fordeclaration for declaration fordeclaration for

parameterparameter Pass-by-ValuePass-by-Value Pass-by-ReferencePass-by-Reference

simple var. int cost int& pricearray impossible int myArray[ ]

array const int source[ ]

1-D Array Review

An array is a structured data type

1st element is “arrayName subzero”

Array Declarationint myArray [9];

Array Initializationint myArray [9 ] = { 9, 9, 9, 8, 7, 6, 5, 4,

3};

Array Element ReferencemyArray [7]; // value = 4 *

99

1-D Array Review

Arrays are always passed by reference, unless const added to the formal parameter.

Array in a Function Prototypevoid myFunction(int [9]);

Array in a Function CallmyFunction(myArray);

Array in a Function Headervoid myFunction(int anyArrayName[9])

optional

Two Dimensional Arrays

a everything about one dimensional arrays applies

a sometimes referred to as a table

a has rows and columnsex. multiplication table

2-D Array Declaration

Syntax

dataType arrayName [[ ConstIntExpression ]] [[ ConstIntExpression ]]

Example

int highTemp [52] [7];double matrix [8] [8]; // checker boardint roomSchedule [237] [13];

2-D Array Initialization

int nums [3] [2] = {7, 4, 1, 8, 5, 2}

int roomsPSF[3] [7] = { {17, 18,19, 110, 111, 112, 113},

{27, 28, 29, 210, 211,212, 213},{37, 38, 39, 310, 311, 312, 313} };

2-D Array Initialization

double ATtoCG[2] [3] = {.74, .79, .76, .83, .65, .89};

double ATtoCG[2] [3] = { {.74, .79, .76}},

{.83, .65, .89} };

int scores[4] [3] = {210, 198, 203, 188, 200, 224, 220, 217, 211, 194, 197, 189};

2-D Array Initialization

You can assign values to individual elements:

ATtoGC [0] [0] = 0.74;

ATtoGC [0] [1] = 0.79;

ATtoGC [0] [2] = 0.76;

ATtoGC [1] [0] = 0.83;

ATtoGC [1] [1] = 0.65;

*

ATtoCG [1] [2] = 0.89;

Accessing a 2-D Array

a very similar to creating a multiplication table.

a use nested loops.outer for loop was for the rowsinner for loop was for the columns

Loading a 2-D Array

a The Multiplication Table

for (row =1; row <=10; row++){

cout <<setw(5)<<row<<" ";forfor (column=1; column <= 10; column++)

cout << setw(5)<< column*row;cout << endl;

}

Loading a 2-D Array

int scores [4][3];

for(row=0; row<4; row++)for(col=0; col<3; col++){

cout<<"Enter the value :";cin>>scores[row][col];

}

Loading a 2-D Array

scores [0][0] [2][0] [0][1] [2][1] [0][2] [2][2]

[1][0] [3][0] [1][1] [3][1] [1][2] [3][2]

[row][col] = somevalue;

Displaying a 2-D Array

int scores [4] [3];

for(row=0; row<4; row++){

for(col=0; col<3; col++) cout << setw(6) << scores[row][col];cout << endl; // new line for each row

}

Displaying a 2-D Array

Output210 198 203188 200 224220 217 211194 197 189

Functions and 2-D Arrays

int test[7][19]; // declaration

find_min(test); // function call

int find_min(int num [7][19]) // funct. header

* * * *

char code[26][10];char code[26][10];

obtain(code);obtain(code);

char obtain(char key [26][10])char obtain(char key [26][10])

Local vs. Global

No difference

““One might as well say he One might as well say he has sold when no one has has sold when no one has bought as to say he has bought as to say he has taught when no one has taught when no one has

learned.”learned.”

John Dewey