CS211 - Algorithms and Data Structures II

Department of Computer Science, NUIM



T Naughton, NUIM

Lab Exam 2







Problem 2A.1



#include<iostream>



void main(void){

  int n;    // input from user

  int row;  // counter for rows

  int counter;



  cout << endl << endl << "Please enter a nonegative integer:" << endl;

  cin >> n;



  cout << endl << "Here we go:" << endl;



  /*

  ** Write out the upper triangle. This will entail, at each row,

  ** writing out (row) spaces and (n - row) stars.

  */

  row = 0;

  while(row < n){



    // write out the correct number of spaces

    counter = 0;

    while (counter < row) {

      cout << ' ';

      counter++;

    }



    // write out the correct number of stars

    counter = row;

    while (counter < n) {

      cout << '*';

      counter++;

    }



    cout << endl;

    row++;

  }



  /*

  ** Write out the lower triangle. This will entail, at each row,

  ** writing out (n-row-1) spaces and (row+1) stars.

  */

  row = 0;

  while(row < n){



    // write out the correct number of spaces

    counter = 0;

    while (counter < (n-row-1)) {

      cout << ' ';

      counter++;

    }



    // write out the correct number of stars

    counter = 0;

    while (counter < (row+1)) {

      cout << '*';

      counter++;

    }



    cout << endl;

    row++;

  }



  cout << "Goodbye!" << endl;

}









Problem 2B.1



#include<iostream>



void main(void){

  int n;       // input from user

  int count1;  // counter for stars & rows

  int count2;  // counter for spaces



  cout << endl << endl << "Please enter a nonegative integer:" << endl;

  cin >> n;



  cout << endl << "Here we go:" << endl;



  /* write first line

  */

  count1 = 0;

  while(count1 < n){

    cout << '*';

    count1++;

  }

  cout << endl;



  /* write middle lines

  */

  count1 = 0;

  while (count1 < (n-2)){

    count2 = 0;

    cout << '*';

    while (count2 < (n-2)){

      cout << ' ';

      count2++;

    }

    cout << '*';

    cout << endl;

    count1++;

  }



  /* write last line

  */

  count1 = 0;

  while(count1 < n){

    cout << '*';

    count1++;

  }

  cout << endl;



  cout << endl << "Goodbye!" << endl;

}







Problem 2C.1



#include<iostream>



void main(void) {

  int n;    // input from user

  int row;  // counter for rows

  int counter;



  cout << endl << endl << "Please enter a nonegative integer:" << endl;

  cin >> n;



  cout << endl << "Here we go:" << endl;



  /*

  ** At each row, write a star, a space, and (n-row) stars.

  */

  row = 0;

  while (row < n) {

    cout << "* ";

    counter = 0;

    while (counter < (n-row)) {

      cout << '*';

      counter++;

    }

    cout << endl;

    row++;

  }

  cout << "Goodbye!" << endl;

}







Problem 2A.2



int findhighestlessthan100(int * list, int len){

  /* This function returns the index of the element with the

  ** highest value in 'list' that is less than 100. 'list' is

  ** an integer array of length 'len'.

  ** If no suitable values are found then an index to the first

  ** element is returned.

  */

  int highest; // the index with the highest value < 100

  int count;



  highest = 0;



  count = 1;

  while (count < len){

    if ((list[count]>list[highest]) && (list[count]<100)){

      highest = count;

    }

    count++;

  }

  return highest;

}





Problem 2C.2 (Note: One can also solve this problem using the

             absolute function abs() from #include<stdlib.h>)



int findclosestto10(int * list, int len){

  /* This function returns the index of the element in 'list'

  ** that has a value closest to 10. 'list' is an integer

  ** array of length 'len'.

  ** If several values are equidistant from 10 then the first

  ** one encountered is returned.

  */

  int closest; // the element with a value closest to 10

  int diff;    // the difference between list[closest] and 10

  int newdiff; // the difference between list[count] and 10

  int count;



  closest = 0;

  if (list[closest]>10){

    diff = list[closest] - 10;

  } else {

    diff = 10 - list[closest];

  }

  count = 1;

  while (count < len){

    if (list[count]>10){

      newdiff = list[count] - 10;

    } else {

      newdiff = 10 - list[count];

    }

    if (newdiff<diff){

      diff = newdiff;

      closest = count;

    }

    count++;

  }

  return closest;

}





Problem 2B.3



#include<iostream>



void readints(int * array, int len);



/* This program reads 10 integers from the user and stores them

** in an array. Using a second array of type double of length 2,

** the program stores the sum and the average of the list of

** integers. Finally, the program outputs the sum and average.

*/



void readints(int * array, int len){

  int count;



  cout << endl << endl << "Please enter " << len;

  cout << " integers, one per line:" << endl;

  count = 0;

  while (count < len){

    cin >> array[count];

    count++;

  }

}



void main(void){

  const int len = 10;

  int array[len];     // holds 10 integers

  double info[2];     // holds sum and mean

  int count;



  readints(array, len);



  info[0] = double(array[0]);

  count = 1;

  while (count < len){

    info[0] = info[0] + double(array[count]);

    count++;

  }



  info[1] = info[0] / double(len);



  cout << endl << "Sum is " << info[0] << endl;

  cout << "Average is " << info[1] << endl;

}





Problem 2C.3



#include<iostream>



void readints(int * array, int len);



/* This program reads 31 integers from the user and stores them

** in an array. Using a second array of type int, of length 31,

** the program stores half the value of each of the first

** array's integers. Finally, the program outputs each int int

** pair where a rounding error has occurred.

*/



void readints(int * array, int len){

  int count;



  cout << endl << endl << "Please enter " << len;

  cout << " integers, one per line:" << endl;

  count = 0;

  while (count < len){

    cin >> array[count];

    count++;

  }

}



void main(void){

  const int len = 31;

  int array[len];     // holds integers

  int half[len];      // holds half of values in array[]

  int count;



  readints(array, len);



  count = 0;

  while (count < len){

    half[count] = array[count] / 2;

    count++;

  }



  cout << endl << endl << "Rounding errors occurred with the";

  cout << " following pairs:" << endl;

  count = 0;

  while (count < len){

    if ((half[count]*2) != array[count]){

      cout << array[count] << ' ' << half[count] << endl;

    }

    count++;

  }

}