Thread: thinking process

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Using the command sequence from message #27 and the code from message #55, after the first command is given, what is stored for matrix A? Please explain why you think so. Or use your debugger to step through the code and see what is stored for A.

well at the end of the if statement of 'A' it is freed so I am guessing nothing is stored. But that free is also necessary because if a person simultaneuosly writes A 2 2 1 2 3 4 and then A 2 2 1 2 3 4 then I only want the second one for A to be stored and that is only possible if I free the first one

So when do you want to free the matrix A? After the first one or when you get the second one? How can you tell if you already have a matrix A (or B or C or D)?

I should free it after the second one is assigned but I dont know how I can tell if there is already a matrix. What can I do?

Why isn't my multiplication function working its giving me a segmentation fault?

Code:

void matrix_multiply( int **A, int **B, int row_size1, int col_size1)
{
  int mult[10][10];
  int i,j,k;
  for(i=0;i<row_size1;i++)
    {
      for(j=0;j<col_size1;j++)
        {
          mult[i][j]=0;
        }
    }
          for(k=0;k<col_size1;k++)
            {
              mult[i][j] = mult[i][j]+ A[i][k]*B[k][j];
            }
          for(i=0; i<row_size1; i++) {
            for(j=0; j<row_size1; j++) {


          printf("%d\t",mult[i][j]);
            }
      printf("\n");
          }
}

Originally Posted by zafy

storing my matrices in an array.. so you mean indexing?
I haven't really done indexing before if you could provide me with a link for me to look over.

And what do you think you are doing with all your matrices????

Originally Posted by zafy

Also no i don't know which type this array should have.
but i like this method you suggested and want to try it

If you are still interested I give you a hint:
Assume you have 4 integer variables A, B, C and D. Now show me how you would declare these variables, declare an additional array which can contain 4 integers and then assign each of the 4 variables to an element of the array. All in all I want you to show me 9 lines: 5 declarations and 4 assignments (one declaration/assignment per line).

If you are able to do this, you should be able to a) know which type the matrices array should have and b) how to use it with your 4 matrices.

If you can't do this, I can assure you the assignment you have to do is way over your capability.

Bye, Andreas

After many strenous hours THANK GOD I got it!
still alot of glitches here and there but... it's working
thanks all

Code:

#include<stdio.h>
#include <stdlib.h>


void matrix_display(int **A, int row_size1, int col_size1);
void matrix_free(int **A, int row_size1);
int **matrix_alloc(int row_size1, int col_size1);
void matrix_fill(int **A, int row_size1, int col_size1);
void matrix_add( int **A, int **B, int row_size1[], int col_size1[],int,int);
void matrix_multiply( int **A, int **B, int row_size1[], int col_size1[],int,in\
t);
void matrix_transpose( int **A, int row_size1[], int col_size1[], int);




int main(void)
{
 int row_size1[5],col_size1[5],flag=1;
  int **A = NULL;
  int **B = NULL;
  int **C = NULL;
  int **D = NULL;
  int **p1, **p2;
  char c,k1,k2;


  do {
    printf("\ncmd > ");
    c = getchar();
 if (c == 'A') {
      scanf("%d %d", &row_size1[0], &col_size1[0]);
      A = matrix_alloc(row_size1[0],col_size1[0]);
      matrix_fill(A,row_size1[0],col_size1[0]);
      matrix_display(A,row_size1[0],col_size1[0]);
      //    matrix_free(A,row_size1);
    }
     if (c == 'B') {
      scanf("%d %d", &row_size1[1], &col_size1[1]);
      B = matrix_alloc(row_size1[1],col_size1[1]);
      matrix_fill(B,row_size1[1],col_size1[1]);
      matrix_display(B,row_size1[1],col_size1[1]);
      // matrix_free(B,row_size1);


    }
    if (c == 'C') {
      scanf("%d %d", &row_size1[2], &col_size1[2]);
      C = matrix_alloc(row_size1[2],col_size1[2]);
      matrix_fill(C,row_size1[2],col_size1[2]);
      matrix_display(C,row_size1[2],col_size1[2]);
      //      matrix_free(C,row_size1);


    }
 if (c == 'D') {
      scanf("%d %d", &row_size1[3], &col_size1[3]);
      D = matrix_alloc(row_size1[3],col_size1[3]);
      matrix_fill(D,row_size1[3],col_size1[3]);
      matrix_display(D,row_size1[3],col_size1[3]);
      // matrix_free(D,row_size1);


      }
    int num1, num2;
     if ( c == '+'){
 scanf(" %c %c", &k1, &k2);
       num1= k1-65;
       num2=k2-65;
       if (k1=='A')
         p1 = A;
       else
         if (k1=='B')
           p1= B;
         else
           if (k1 == 'C')
             p1 = C;
           else
             if (k1=='D')
               p1 =D;
       if (k2=='A')
         p2 = A;
       else
         if (k2=='B')
           p2= B;
         else
           if (k2 == 'C')
             p2 = C;
           else
             if (k2=='D')
               p2 =D;
       /* A = A + B */
       matrix_add(p1, p2, row_size1, col_size1,num1,num2);
  matrix_free(A,row_size1);
       matrix_free(B,row_size1);
     }
     if ( c == '*'){
       scanf(" %c %c", &k1, &k2);
       printf ("%c %c\n",k1,k2);
       num1= k1-65;
       num2=k2-65;
       if (k1=='A')
         p1 = A;
       else
         if (k1=='B')
 p1= B;
         else
           if (k1 == 'C')
             p1 = C;
           else
             if (k1=='D')
               p1 =D;
       if (k2=='A')
         p2 = A;
       else
         if (k2=='B')
           p2= B;
         else
           if (k2 == 'C')
             p2 = C;
           else
             if (k2=='D')
               p2 =D;
  matrix_multiply(p1, p2, row_size1, col_size1,num1,num2);




     }
     if ( c == '^'){
       scanf(" %c", &k1);
       printf (" %c\n",k1);
       num1= k1-65;
 if (k1=='A')
         p1 = A;
       else
         if (k1=='B')
           p1= B;
         else
           if (k1 == 'C')
             p1 = C;
           else
             if (k1=='D')
               p1 =D;
  matrix_transpose(p1, row_size1, col_size1,num1);
  }




    if (c == '$') {
      flag = 0;
    }
  }


  while (flag == 1);
  return 0;
}


void matrix_display(int **A, int row_size1, int col_size1)
{
  int i, j;
 printf("The required matrix is\n");
  for (i = 0; i < row_size1; i++) {
    for (j = 0; j < col_size1; j++)
      printf("%d ", A[i][j]);
    printf("\n");
  }
}


void matrix_free(int **A, int row_size1)
{
  int i;
  for (i = 0; i < row_size1; i++) {
    free(A[i]);
  }
  free(A);
}


int **matrix_alloc(int row_size1, int col_size1)
{
  int i;
 int **result = malloc(row_size1 * sizeof(int *));
  for (i = 0; i < row_size1; i++) {
    result[i] = malloc(col_size1 * sizeof(int));
  }
  return result;
}


void matrix_fill(int **A, int row_size1, int col_size1)
{
  int i, j;
  printf("Enter matrix of %d rows and %d columns\n", row_size1, col_size1);
  for (i = 0; i < row_size1; i++) {
    for (j = 0; j < col_size1; j++) {
      scanf("%d", &A[i][j]);
    }
  }
}
void matrix_add( int **A, int **B, int row_size1[], int col_size1[],int x,int y\
)
{
 if (row_size1[x]!= row_size1[y]||col_size1[x]!=col_size1[y])
    {
      fprintf (stderr,"Matrix incompatible for addition\n");
      exit (1);
    }
  int i,j;
  for(i=0;i<row_size1[x];i++)
    for(j=0;j<col_size1[x];j++)
      A[i][j]=A[i][j]+B[i][j];


  printf("\n\nThe Sum Of Matrices Is:");
  for(i=0;i<row_size1[x];i++){
    printf("\n");
    for(j=0;j<col_size1[x];j++)
      printf("%d ",A[i][j]);
  }
}
void matrix_multiply( int **A, int **B, int row_size1[], int col_size1[],int x,\
 int y)
{
  printf ("\n\n");
  int mult[10][10];
  int i,j,k;
  printf ("lets see");
    for(i=0;i<row_size1[x];i++)
    {
      for(j=0;j<col_size1[y];j++)
        {
          mult[i][j]=0;
        }
    }
 for(i=0; i<row_size1[x]; i++) {
            for(j=0; j<col_size1[y]; j++) {
              for(k=0;k<row_size1[y];k++)
                {
                  mult[i][j] = mult[i][j]+ A[i][k]*B[k][j];
                  //printf("%d\t",mult[i][j]);
                }
              printf ("%d\t",mult[i][j]);
            }
      printf("\n");
          }
}
void matrix_transpose( int **A, int row_size1[], int col_size1[], int x)
{
  printf ("\n\n");
  int transpose [10][10];
int i,j;
for( i = 0 ; i < row_size1[x] ; i++ )
  {
 for( j = 0 ; j < col_size1[x] ; j++ )
      {
        transpose[j][i] = A[i][j]; //defining the transpose
      }
  }
printf("Transpose of entered matrix :-\n");
for( i = 0 ; i < col_size1[x] ; i++ ) //changing entries of the for loop t
  {
    for( j = 0 ; j < row_size1[x] ; j++ )
      {
        printf("%3d\t",transpose[i][j]);
      }


    printf("\n");
  }
}

dont mind the indenting I am just so excited its working and I can finally show you guys