Friday, December 29, 2006

Should array indices start at 0 or 1? My compromise of 0.5 was rejected

without, I thought, proper consideration.

- Stan Kelly-Bootle

Assignment 2 is up.

Programming Tip: Choosing formal parameter names

#include <stdlib.h>

int rand(void)

List of marksList of names…

Arrays offer a convenient means of grouping together several related variables

Arrays

Declaring an array

type array_name[size]; allocates memory for size variables index of first element is 0 index of last element is size-1 size must be a constant

Declaring an array- ExampleExample: 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]

Arrays One- dimensional arrays

type var_name[size];

int sample[10];

double d[30];

char ch[100];

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};

Initializing ArraysWhat is wrong with the following?

int num=10;

int iarray[num];

int size;

cin>>size;

int myArray[size];

double dArray[5]={3.2, 4.5, 6.7, 324.0, 45.8, 23.1, 34.9};

Assigning values to an array•Example

int list[10];int count, i;cin >> count;for(int i=0; i<count; i++)

cin >> list[i];

•for loops are often used to assign values to an array

Assigning values to an array•Example

int list[10];int count, i;cin >> count;for(int i=0; i<count; i++)

cin >> list[i];

What if count >9?

Assigning values to an arrayint main() { // this reserves 10 integer elements

int sample[10]; int t; // load the array for(t=0; t<10; ++t)

sample[t]=t; // display the array for(t=0; t<10; ++t)

cout << sample[t] <<“ “; return 0;} //output ?

Arrays Output is:

0 1 2 3 4 5 6 7 8 9

Summarize ArraysAn 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 variablesAll variables stored in an array are of the

same data typeAn individual variable within an array is

called an element of the array

Summarize Arrays In C++ all arrays are stored in contiguous memory

locations

An index describes the position of an element within an array.

In C++ all arrays have zero as the index of their first element.

The name of the array is the address of the first element. The index is the offset

Arrays Total size of an array in bytes?Total bytes = number of bytes in type x number of

elementse.g. int sample[10];

sizeof operator

Arrays int a[10];

cout<<sizeof(a)<<endl;

cout<<sizeof(a[0])<<endl;

cout<<sizeof(int)<<endl;

double d[10];

cout<<sizeof(d)<<endl;

cout<<sizeof(d[0])<<endl;

cout<<sizeof(double)<<endl;

Arrays 40

4

4

80

8

8

Arrays int main()

{

int i, min_value, max_value;

int list[10];

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

list[i] = rand();

cout<<list[i]<<" ";

}

Arrays // find minimum value

min_value = list[0];

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

if(min_value>list[i]){

min_value = list[i];

}

}

cout << "minimum value: " << min_value << “\n”;

Arrays // find maximum value

max_value = list[0];

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

if(max_value<list[i]){

max_value = list[i];

}

}

cout << "maximum value: " << max_value << '\n';

return 0;

}

Arrays int a[10], b[10];

// ...

a = b; // error -- illegal

/*So how do we make the contents of one array same as the other?*/

Arrays // An incorrect program.

int main()

{

int crash[10], i;

for(i=0; i<100; i++)

crash[i]=i;

return 0;

}

Arrays - No bounds checking // An incorrect program.

int main()

{

int crash[10], i;

for(i=0; i<100; i++)

crash[i]=i;

return 0;

}

Sorting an arrayLots of applications require sortingAlgorithm for sorting