Deck 5: Arrays

Question 1

Given the two C++ array declarations:
int a[10],b[10];
You can successfully compute one array,say a,then assign b to a:
a = b;

Answer 1

False

Question 2

Arrays in C++ may have several different types stored in them.

Answer 2

False

Question 3

Distinguish the use of the square brackets [] in a definition of an array and their use for access to some indexed variable of the array.

Answer 3

In the definition of an array,for example,int array[10];the [] are used to define the array,the number between the brackets specifies the declared size,that is,it specifies how many indexed variables are being defined.This could be any number.
In the access to an indexed variable,for example,array[5] = 14;the number between the brackets specifies which of the indexed variables is being accessed.This must be between 0 and one less than the declared size of the array.Technically,the [] are called the subscripting operator.

Question 4

When using an array,it is perfectly legal to access indexed variables with index values less than 0 or greater than or equal to the declared size of the array.

Question 5

Indexed variables for an array are stored wherever the computer finds memory for the first indexed variable,then the next one is stored next to the first if there is space,and someplace else if not.

Question 6

To call a function with an array parameter,write the array argument as the array name followed by empty square brackets,as in f(a[],7); (The first argument is an array a,the second is the size. )

Question 7

In the sequential search algorithm,items are examined alternately,odd then evens,in order to find whether the target value is in the array (and if the target is present,to the index of the target. )

Question 8

The programmer should always use a defined constant in an array declaration.

Question 9

C++ arrays check for out-of-range index values.

Question 10

A for-loop is a convenient way to step through an array.

Question 11

With arrays,indices start at any number the programmer chooses to indicate in the definition.

Question 12

Consider the array declaration,int x[20];.There is no memory allocated for x[20].

Question 13

Write a C++ code fragment that is assumed to be embedded in an otherwise complete and correct program.You are to assume the user has been prompted (so you don't have to)for (exactly)20 values of type int to be read from the keyboard,You are to use this input to fill an array.Do not write a full program,just the code fragment to do this.Do give declarations of the array and any variables you use.

Question 14

An array behaves like a list of variables each of which is of the same type and for which there is a uniform,convenient naming convention that can be declared in a single line of code.In the explanation,give an example of declaration and access.

Question 15

If you need an array with more than one index,you can use a multidimensional array,which is actually an array of arrays.In the explanation,declare an array of doubles with 2 rows and 5 columns.

Question 16

If we want to find the median of 100 scores,we need 100 separate variables to hold the data..

Question 17

In a sorting an array,the items in the array are rearranged so that
for all j and k,if j < k,then array[j]<=array[k]

Question 18

In the definition,double d[10] = {0.0};only d[0] is initialized to zero,the rest are uninitialized,just like x in the definition double x;

Question 19

Describe the difference in the meaning of the 5 in int x[5];and the meaning of the 4 in x[4].What are the meanings of the int,the [5] and the [4]?

Question 20

Give the syntax of an array declaration.Mention the base type and declared size.

Question 21

What is the output of the following code?
#include
int main()
{
using namespace std;
double a[3] = {1.1,3.3,2.2};
cout << a[0] << " " << a[1] << " " << a[2] << endl;
a[1] = a[2];
cout << a[0] << " " << a[1] << " " << a[2] << endl;
}

Question 22

Explain the error in the following code.You may give the warning message,or error message,your compiler might give for the following error,or you may describe the error.However you present the error,you must explain clearly what is wrong.
#include
//Test question
void show_array(int ar[],int size)
{
using namespace std;
for(int i = 0;i < size;i++)
cout << ar[i] << " ";
cout << endl;
}
int main()
{
const int a[6] = {2,4,2,3,5};
show_array(a,6);
//...
}

Question 23

Here is a list of 8 numbers.Use the selection sort algorithm to sort this list.Fill in this table with each iteration of the loop in the selection sort algorithm.Mark the place from which you are looking for the 'next smallest element'.In this display,the upper numbers are the indices,the lower numbers are in the corresponding positions.Use the several rows provided to show the sequence of steps.
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
8 6 10 2 16 4 18 14
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-
0 1 2 3 4 5 6 7
|------|------|------|------|------|------|------|-

Question 24

Consider the declaration
double a[10] = {1.2,2.1,3.3,3.5,4.5,7.9,5.4,
8.7,9.9,1.0};
Write a function named out_of_order that will test this array for the condition
a[0] <= a[1] <= a[2] <= ...
The function returns a -1 if the elements are not out of order,otherwise it returns the index of the first element that is out of order.
Explain what you do to avoid out of bounds array access.

Question 25

Given the definition and code fragment: int matrix[2][3];
Int k = 0;
For(int i =0;i < 3;i++)
For (int j=0,j < 4;j++)
Matrix[i][j] = k++;
The value of matrix[0][0] is

A)0
B)1
C)2
D)3
E)4

Question 26

Given the array declaration,int a[20];The first element is written as:

A)a[1]
B)a[0]
C)a
D)a[20]
E)a[19]

Question 27

Suppose we want an array to satisfy the condition,
a[0] <= a[1] <= a[2] <= ...
And suppose this code is written to implement a test of this condition
#include
using namespace std;
int main()
{
double array[10] = { 1,2,3,4,5,6,7,8,9,10 };
// assume the array is filled somehow.
for(int i=0;i < 10;i++)
if (array[i] > array[i+1])
cout << "Array elements " << i << " and "
<< i + 1 << " are out of order.\n";
}
When this is run,we sometimes get the following puzzling output:
Array elements 9 and 10 are out of order.
Even more puzzling,sometimes we don't get this output.
Why?

Question 28

Insert const before .any of the following array parameters that can be changed to const.
void output(double a[],int size);
//Pre: a[0] through a[size-1] have values set.
//Post: a[0] through a[size-1] have been displayed on the screen.
void dropOdd(int a[],int size);
//Pre: a[0] through a[size-1] have values set.
//Post: All odd numbers in a[0] through a[size-1] have //been changed to 0.

Question 29

What is the output of the following code (assuming it is embedded in a correct and complete program)? char letter[5] = {'o','k','c','e','g'};
For(int i = 4;i >= 0;i-- )
Cout << letter[i];
Cout << endl;
Choices:

A)okceg
B)gecko
C)ecko followed by a character from an out of bounds access.
D)kceg followed by a character from an out of bounds access.
E)Correct answer not listed.Specify what the output is.

Question 30

Write the selection sort algorithm for an array of int in C++.You are to assume that there are predefined functions swapValues and indexOfSmallest,that is do not write these functions.However,you must write declarations with pre and post conditions for these functions.

Question 31

What is the problem with this code?
int .array[5];
>>Delete the dot
for (int index = 1;index <=5;index++)
array[index] = index /2;

Question 32

Assume you have a swap routine in place for doubles.Write a routine calls swap that reverses the entries in an array of doubles.Use this function declaration.
void reverse( double a,int size);
Carry out your reversal in place,do not make a local copy of the array