CISC106-010, Fall 2007 12/7/2007

Answers for Practice Questions dated 12/7/2007

Contents

C++ arrays

Various topics in C++

C++ arrays

Look at the practice questions at http://www.udel.edu/CIS/106/iaydin/07F/practice/practice_2007_12_3.txt

The answers are in the link above also.

Various topics in C++

A1.

#include <iostream.h>

using namespace std;

int main(){

// error1: declare the integer i. Remember, C++ you

// have to declare a variable or function prototype

// before using it.

int i;

i = 55;

// error2: you need to use << operator with cout

// error3: you need to end your executable statements

// in C++ with a semi-colon

cout << endl << "my number is: " << i << endl;

return 0;

}

A2.

// isSeven() function returns true if the number i is 7

// inputs:

// i: the number to test

// outputs:

// true if i is 7 else return false.

bool isSeven(int i)

{

bool result;

result = false;

// run-time error: you need to use == sign to

// test equality!

if (i == 7)

result = true;

// compile-time error: Since the return type of this

// function is not void,but a bool, you need to

// return a boolean before exiting the function.

// In this case, you need to return result.

return result;

}

A3.

#include <iostream.h>

using namespace std;

// declaring the function prototype

bool isEven(int i);

int main(){

int i;

cout << “Please enter a number: ” ;

cin >> i;

if ( isEven(i) )

{

cout << endl << "number " << i << " is an even number" << endl ;

}

else

{

cout << endl << "number " << i << " is an odd number" << endl ;

}

return 0;

}

A4.

bool isOdd(int i)

{

bool result;

if ( isEven(i) )

{

result = false;

}

else

{

result = true;

}

return result;

}

A5.

for (int k = 0 ; k <10 ; k++)

{

cout << k << endl;

}

C++ vs. MATLAB

A1.

// addElements() function: returns the sum of the integers

// in integer array x

// inputs:

// x: the integer array

// len: the number of elements in the array

// outputs:

// sum of the integers in integer array x

int addElements(int x[], int len)

{

// important note: make sure you initialize sum to zero,

// so that if len is 0, then your function returns

// the right sum (which is zero).

int sum = 0;

// important note: make sure j starts from zero and

// ends at len-1, so that you can add up all the elements

// of array x. Remember, (1) C++ array indices start from

// zero (2) the last element of the array x is x[len-1].

for (int j = 0; j < len; j++)

{

sum = sum + x[j];

}

// important note: once you calculate the sum,

// you have to explicitly return it in

// the return statement.

return sum;

}

A2.

>> clear

>> v = [15 0 -5 10]

>> mysum(v)

A3.

int main(){

const int SIZE = 4;

int A[SIZE] = {5, 60, -10}

int sum;

// write the function call below

sum = addElements(A, len);

cout << endl << "Sum of the elements of array A is: " << sum << endl;

return 0;

}

A3.

The screen output for the MATLAB code piece is:

oooox

A C++ while loop doing the same can be

// declare your loop variable

int i = 1;

// count 4 times in the loop

while (i <= 4)

{

// remember C++ strings are written using double-quotes

cout << “o”;

}

//print x to the screen and endl to print a line-break

cout << “x” << endl;

A4.

The screen output for the MATLAB code piece is:

A C++ for loop doing the same can be

// declare i in the for loop

// use i to count 5 times, with the for loop

for (int i = 1; i <= 5; i = i+1)

{

// use double-quotes for printing a string to the

// screen and endl to print a line-break

cout << “o” << endl;

}

cout << “x” << endl;