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Ternary/Conditional Operator (?:)

Syntax

(condition) ? (if_true) : (if_false)

Example

int largest = ((a > b) ? a : b);

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Ternary/Conditional Operator (?:)

int x=0;

(x==0) ? (x=20) : (x=30);

cout

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Ternary Operator Vs If Statement

The ternary operator is an expression

whereas

the if structure is a statement.

A ternary operator expression's result can beassigned to a variable, the results of an if

statement cannot.

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Ternary Operator Vs If Statement

The advantage that the if statement has is

that you can have multiple clauses, where

as with the ternary operator you can haveonly two.

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Arrays offer a convenient

means ofgrouping together

several related variables

Arrays

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List of marks

List of names

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Declaring an array

typearray_name[size];

allocates memory for sizevariables

index of first element is 0

index of last element is size-1

sizemust be a constant

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Declaring an array- Example

Example: int list[10]; allocates memory for 10 integer variables index of first element is 0

index of last element is 9

C++ does not perform any bounds checking on arrays

list[1]

list[0]

list[9]

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Arrays

One- dimensional arrays

type var_name[size];

int sample[10];

double d[30];

char ch[100];

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Initializing Arrays

Arrays can be initialized at the time they are

declared.

Examples:double taxrate[3] ={0.15, 0.25, 0.3};

int num[10] ={0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

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C++ does not bound check arrays

int intArray[5]={1, 2, 3, 4, 5};

for (int i=0; i

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Lecture 20

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Assigning values to an array

Exampleint list[10];

int count, i;

cin >> count;for(int i=0; i> list[i];

for loops are often used to assign values to an array

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Assigning values to an arrayExample

int list[10];

int count, i;

cin >> count;

for(int i=0; i> list[i];

What if count >9?

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Assigning values to an array

int main() {// this reserves 10 integer elements

int sample[10];

int t;

// load the array

for(t=0; t

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Arrays

Output is:

0 1 2 3 4 5 6 7 8 9

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Summarize Arrays

An array is an indexed data structure

An element of an array is accessed using

the array name and an index

An array stores a collection of variables

All variables stored in an array are of the

same data type

An individual variable within an array is

called an elementof the array

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Summarize Arrays

In C++ all arrays are stored in contiguous memory

locations

An index describes theposition of an element within

an array.

In C++ all arrays have zeroas the index of their first

element.

The name of the array is the address of the first

element. The index is the offset

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Arrays

Total size of an array in bytes?

Total bytes = (number of bytes in type) x (number ofelements)

e.g. int sample[10];

sizeof operator

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Arrays

int a[10];

cout

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Arrays

40

4

4

808

8

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Arrays Review

Arrays used for grouping of related variables.int a1; int a[5];

int a2;

int a3;int a4;

int a5;

Individual elements of array accessed byindices.

Easier to use in loops.

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Arrays Review

int a[5] = {10, 20, 30, 40, 50};a[0] is 10

a[1] is 20

a[2] is 30

a[3] is 40

a[4] is 50

No boundary checking of arrays because of

efficiency reasons. Error checking can slow down the program

execution.

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A variable is a named memory location that may

be assigned a value.

10

20

30

40

50

a[0]

a[1]

a[2]

a[3]

a[4]

0x0012F578

0x0012F57C

0x0012F580

0x0012F584

0x0012F588

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What is wrong here?

const int x;

A

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Arraysint myArray[3];

myArray[0]=0;

myArray[1]=1;

myArray[2]=2;

ORint myArray[3] = {0,1,2};

OR

int myArray[] = {0,1,2};

int myArray[3]={}; //intializes all elements to 0int myArray[]={};//Error:cant allocate an array of constant size 0

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Arrays

int main()

{

int i, min_value, max_value;

int list[10];

for(i=0; i

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Arrays

// find minimum value

min_value = list[0];

for(i=0; ilist[i]){

min_value = list[i];

}

}cout

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Arrays// find maximum value

max_value = list[0];

for(i=0; i

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Arrays

int a[10], b[10];

// ...

a = b; // errorillegal.

/*The name of the array is the address of the first

element. The index is the offset

So how do we make the contents of one array

same as the other?*/

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Arrays

int a[5]={1,2,3,4,5}, b[5];

for (int i=0; i

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Arrays

Finding size of an array

int a[]= {1,2,4,5,7,9,12};

cout

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Lecture 21

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Strings

One dimensional arrays are used to create

character strings

In C++, a string is defined as a character

array that is terminated by a null

A null is specified using \0 and is zero

Because of the null terminator, it is

necessary to declare a character array to be

one characterlonger than the largest stringit will hold.

Ch A

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Character Arrays

char word[6] = fruit; //word has size 6

char list[6] = {f,r,u,i,t, \0};

//list of characters, not a string

Not necessary to add null terminator at end of string

constants.

Ch A

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Character Arrays

char word[] = fruit;//word has size 6

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What is wrong with the following?

char name[5]="class";

int MyArray[];

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'a' and "a" are different

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Null String

""

Only contains null terminator.

R di t i f k b d

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Reading strings from keyboard

The easiest way to read a string entered from

the keyboard is to make a characterarrayint main()

{

char str[80];

cout > str; // read string from keyboard

cout

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Reading strings from keyboard

There is a problem with previous program, if the string has

whitespace characters

// Using gets() to read a string from the keyboard. #include

int main() {

char str[80];

cout

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When you send output to cout, it does not

necessarily get printed immediately. Rather, it

may wait in a buffer until some event, e.g.

buffer full enough, reading from input etc.

Forcing all buffered output to actually be

printed is known as "flushing" the stream. Aflush can be forced by inserting flush into the

stream, or inserting endl.

cout

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HomeWork (hard copy due in

next class) Get string input (of length no greater than

10) from keyboard and store in a char array

usinggets function provided by C++stdio.h

library

Print the inverted string

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HomeWork (hard copy due in

next class) Example:

Input string: my str Output: rts ym

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Sorting an array

Lots of applications require sorting

Algorithm for sorting

Sorting an array

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Sorting an array

double dArray[10]={34, 5.6, 0.9, 345.7, 54.1, 23.5, 2.5,

6.78, 12.4, 13.9};

Sorting an array

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Sorting an arrayint main(void){ const int size=10;

int i, j;

double dArray[size]={34, 5.6, 0.9, 345.7, 54.1, 23.5,2.5, 6.78, 12.4, 13.9};

double temp;

for (i=0; i

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Self Test: Sorting an array

Modify the previous program so that it does not

do in-place sorting, but instead stores the sortedlist in another array.

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Lecture 22


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// Using the bubble sort to order an array.

int main()

{

int nums[10];

int a, b, t;

int size;

size = 10; // number of elements to sort// give the array some random initial values

for(t=0; t

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Self Test: Sorting an array(Simulate)

// This is the bubble sort.

for(a=1; a=a; b--) {

if(nums[b-1] > nums[b]) { // if out of order

// exchange elements

t = nums[b-1];

nums[b-1] = nums[b];nums[b] = t;

}

} // This is the end of the bubble sort.

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Bubble Sort Simulation

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Two Dimensional Arrays

C++ supports multi-dimensional arrays

typearray_name[row_size][column_size]

int matrix[3][4];

row[0]

row[1]

row[2]

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Two dimensional arrays

int array[2][3] = {{1,2,3},

{4,5,6}};

int E[][2]={

1,2,

3,4

};

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Accessing Array Elements

int matrix[3][4];

matrix has 12 integer elements

matrix[0][0] element in first row, first column

matrix[2][3] element in last row, last column

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Two Dimensional Arrays

int jimmy[3][5];

int main() Two Dimensional Arrays

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int main()

{

const int rows=3, cols=4;

int i, j, num[rows][cols];

for(i=0; i

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Output:

1 2 3 45 6 7 8

9 10 11 12

int main()Two Dimensional Arrays

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int main()

{

const int rows=2, cols=6;

int i, j, num[rows][cols];

for(i=0; i

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Output:

1 2 3 4 5 67 8 9 10 11 12

Self Test: Arrays

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Self Test: Arrays

Print the transpose of a 2-D array.

Self Test: Arrays

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Self Test: Arrays

Print the transpose of a 2-D array

for(int i=0; i

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Practice Exercise!

Write down the code to multiply two

matrices of sizes NxM and MxQ

respectively.

Arrays

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Arrays

int a[10] = {1,2,3,4,0,3,4,6,7,8};

int x=3; y=1;

cout

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Arrays

int a[10] = {1,2,3,4,0,3,4,6,7,8};

int x=3; y=1;

cout

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The name of the array is the address

of the first element. It is a constant.

int a[5]={13, 5, 6, 34, 6};cout

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The name of the array is the address

of the first element. It is a constant.

5

346

0x0012FEC4

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char str[]="fruit";

cout

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r

it

fruit

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int twoD[4][2]={

1, 10,

2, 13,

3, 34,

4, 15

};

Picture of array

twoD[1][1] is

twoD[2][0] is

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int twoD[4][2]={

1, 10,

2, 13,

3, 34,

4, 15

};

Picture of array

twoD[1][1] is 13

twoD[2][0] is 3

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Arrays of strings

char strings[6][80]={

"one","two",

{'t','h','r','e','e',\0},

"four",

"five",""

};

Picture of array

cout

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Arrays of strings


"one","two",

{'t','h','r','e','e', '\0'},

"four",

"five",""

};

Picture of array

cout

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Arrays of strings


"one","two",

{'t','h','r','e','e,\0},

"four",

"five",""

};

int i=0;

while(strings[i][0]){

cout

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char str[]="This is CS";

int i=0;while(str[i]){

cout

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T

h

is

i

s

C

S

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What if I insert a zero?

char str[]="This is 0CS";int i=0;

while(str[i]){

cout

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char str[80];

do{

gets(str);

cout

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S g y

strcpy() strcat() strlen() strcmp()

#include strcpy(to, from)

int main()

{char str[80];

strcpy(str, "hello");

cout

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g y

strcpy() strcat() strlen() strcmp()

#include strcpy(to, from)

int main()

{char str[80];

strcpy(str, "hello");

cout

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g y ( )

int main()

{char s1[20], s2[10];

strcpy(s1, "hello");

strcpy(s2, " there");

strcat(s1, s2);

cout

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Output is:hello there

String Library Functions (strcmp)

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g y ( p)

strcmp(s1,s2)compares two strings andreturns 0

if they are equal. If s1 is greater than s2 (dictionaryorder) then a positive number is returned; if it is

less than s2 then a negative number is returned.

cout

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strlen(s) returns the length of s (not counting

null terminator)

int main()

{

char str[80];cout

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char words[3];

strcpy (words,

Now, here is a long string.);

What is wrong here?

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char words[3];

strcpy (words,

Now, here is a long string.);

Will continue to fill whatever memory follows

last indexed variable ofwords, even thoughthis memory may be used for something else.

What is wrong here?

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What is wrong with following?

char str1[80]=i am a string;


if (str1==str2)cout

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if (str1==str2)cout

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char str1[80]="cs";char str2[80];

str2=str1;

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char str1[80]="cs";char str2[80];

str2=str1; //Error

Use strcpy(str2, str1);

Lec19 21 Arrays

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