Thread: please help me to understand the question

Hi guys,

Sorry, can u please explain to me what is the sentence in red saying? I'm working on this problem and can do the previous parts until i reached this part. What is int n supposed to be and how is the function supposed to recognise whether the number needs to be swapped when it only takes in addresses?

This entire question is supposed to arrange all columns in a 3 by 3 matrix in asecending order.

ie.

2 -17 11
-1 11 -7
0 3 -2

to

-1 -17 -7
0 3 -2
2 11 11

Pls help to explain. thanks


Write a function
colSort to sort each column of the table in ascending order.

void colSort(int table[][MAX], int rows, int cols);
Use the following guide in your implementation.

Within the colSort function, declare an array of integer pointers int *listPtr[MAX]; . Write a function getColumn that takes in the original table table, the number of rows, the column index cIndex as well as the listPtr array and fill
the latter with the addresses of all the elements of the column cIndex.

void getColumn(int table[][MAX], int rows, int cIndex, int *listPtr[]);
Write a function ptrSort that takes as argument the listPtr array and sorts the column of the original table via the pointer elements of listPtr.

vovvv void ptrSort(int *listPtr[], int n);

3 functions:

colSort(), getColumn(), and ptrSort(). Instead of sorting the column values directly, the assignment wants your program to sort the values, THROUGH the pointers (and remembering that the pointers point to the values, by dereferencing them with the *).

ok...i'll try that again later..thanks...

i came across this online...can i ask u...if i want to express the following...

gcd (m,n) = m if n=0
= gcd (n, m%n) if n>0

Can this be expressed as gcd= n==0 ? m : m%n

the last part seems wrong....but i cant tell wads wrong...can u help me to edit it...

Originally Posted by jollykiddo

ok...i'll try that again later..thanks...

i came across this online...can i ask u...if i want to express the following...

gcd (m,n) = m if n=0 <<===== This is an syntax error, should be if(n==0) in C
= gcd (n, m%n) if n>0

Can this be expressed as gcd= n==0 ? m : m%n

the last part seems wrong....but i cant tell wads wrong...can u help me to edit it...

You have a function gcd which takes two int's - one is the value that you're searching for the gcd of, and the other is a test int?

Hard to say much about it without seeing the code.

Originally Posted by Adak

3 functions:

colSort(), getColumn(), and ptrSort(). Instead of sorting the column values directly, the assignment wants your program to sort the values, THROUGH the pointers (and remembering that the pointers point to the values, by dereferencing them with the *).

for the previous programmae...i got the listPtr from the the function get column...which i wrote the function as follows...but what's int n? what's input is the function ptrSort expecting?

Code:

void getColumn (int table [][3], int rows, int cIndex. int *listPtr[])
{
        int i=0; 
        for(i=0; i<3; i++)
            listPtr[i]=&(table[i][cIndex])
}

I believe n is the number of the column that is to be sorted. Only one column at any time is being sorted.

Originally Posted by Adak

You have a function gcd which takes two int's - one is the value that you're searching for the gcd of, and the other is a test int?

Hard to say much about it without seeing the code.

Ok...i'll try the assignment in a while...meanwhile...can u advise whether this is correct...thanks

Code:

 
  #include <stdio.h> 
    
   void swap (int *X, int *Y);
   int gcd (int m, int n); 
    
   int main ( ) 
   {   
       int GCD=0; 
       int m=0; 
      int n=0; 
      
      scanf("%d",&m); 
      scanf("%d", &n); 
      
      if (n>m) 
          swap(&m,&n); 
      GCD=gcd(m,n); 
      printf("%d", GCD);
   
      return 0; 
  } 
   
  void swap ( int *X, int *Y) 
  {
      int temp;
      temp= *X;
      *X= *Y;
      *Y= temp;
  }
  
  int gcd ( int m, int n)
  {
      return (n==0)? m : gcd(n,m%n) ;
  }

are there any instances when this code will fail?

so this operator '? :' is to replace if else?