CS211 - Algorithms and Data Structures II

Department of Computer Science, NUIM



T Naughton, CS NUIM

Solutions for Tutorial 2







Problem T2.1



#include<iostream>



/* This program prints out the ascii codes for each of

** the letters of the alphabet.

*/



void main(void){

  char count;



  cout << endl << endl << endl;

  count = 'a';

  while (int(count) <= int('z')){

    cout << count << '\t' << int(count) << '\t';

    count = char(int(count)+1);

  }

  cout << endl;

  count = 'A';

  while (int(count) <= int('Z')){

    cout << count << '\t' << int(count) << '\t';

    count = char(int(count)+1);

  }

}







Problem T2.2



#include<iostream>

//#include<stdlib.h>

//#include<math.h>



bool myeven(int a);

int myabs(int a);



/*

** This quick program implements routines to test for 'even'ness and

** to find the absolute value of an integer.

** It also tests the operation of the sqrt() function. Try entering -4.

*/



bool myeven(int a){

  if ((a % 2) == 0){

    return true;

  } else {

    return false;

  }

}



int myabs(int a){

  if (a < 0){

    a = a * (-1);

  }

  return a;

}



void main(void){

  int input;



  cout << endl << "Please enter an integer:" << endl;

  cin >> input;



  cout << "abs(" << input << ")=" << myabs(input) << endl;



  cout << input << " is ";

  if (!myeven(input)) {

    cout << "not ";

  }

  cout << "an even number." << endl;



  cout << "sqrt(" << input << ")=" << sqrt(input) << endl;



}









Problem T2.3



#include<iostream>



char myuppercase(char letter);



/*

** This program implements a routine to convert a character

** from lowercase to uppercase.

*/



char myuppercase(char letter){

  /* If it is not a lowercase letter (or not a letter at all)

  ** just return it unchanged. Otherwise, add the difference

  ** in ASCII number between upper and lower case numbers.

  ** Note, we don't have to know the set of ASCII numbers, or even

  ** whether 'A' has a higher number than 'a'.

  */

  if ((int(letter) >= int('a')) && (int(letter) <= int('z'))){

    letter = char(int(letter) + (int('A') - int('a')));

  }

  return letter;

}



void main(void){

  char input;

  cout << endl << "Please enter a character:" << endl;

  cin >> input;

  cout << "The uppercase of " << input << " is " << myuppercase(input);

  cout << "." << endl;

}









Problem T2.4



#include<iostream>



/* This program shows two different ways of passing by reference.

** Exchange1 uses the standard pointer rules and preserves

** strong typing conventions. Exchange2 uses a C/C++ trick to make

** code look neater.

** As explained in lectures, I (TJN) have two reasons for

** preferring convention 1.

** 1) Less rules to remember -- convention 1 can be derived from the

**    basic pointer rules. This will be useful if/when coding

**    data structures with pointers to pointers of pointers.

** 2) In the calling function, it is obvious that the parameters will

**    be passed by reference without having to look at the called

**    function's prototype.

*/



void Exchange1(int * elem1, int * elem2){

  int temp;

  temp = *elem1;

  *elem1 = *elem2;

  *elem2 = temp;

}



void Exchange2(int & elem1, int & elem2){

  int temp;

  temp = elem1;

  elem1 = elem2;

  elem2 = temp;

}



void main(void){



  int iarray[2] = {3,4};



  int x = 5;

  int y = 6;



  cout << endl << endl;

  cout << "Swapping variables:" << endl;



  cout << iarray[0] << ' ' << iarray[1] << endl;

  Exchange1(&iarray[0], &iarray[1]);

  cout << iarray[0] << ' ' << iarray[1] << endl;

  Exchange2(iarray[0], iarray[1]);

  cout << iarray[0] << ' ' << iarray[1] << endl;



  cout << endl;

  cout << x << ' ' << y << endl;

  Exchange1(&x, &y);

  cout << x << ' ' << y << endl;

  Exchange2(x, y);

  cout << x << ' ' << y << endl;



}