Pointers

[dan1992]

How to make this program

#include <stdio.h>
#include <conio.h>
#include <math.h>

int main(){
    clrscr();

    for(i=0;i<10;i++)
     for(j=0;j<10;j++)
    printf("a[%d][%d] = %d \n",i,j,a[i][j]);
    printf("cu pointer\n");
    for(i=0;i<10;i++)
    for(j=0;j<10;j++)
    printf("a[%d][%d] = %d \n",i,j,*(p+i));
    getch();
    }

       int a[4][4],b4[3][3],b1[3][3],b2[3][3],b3[3][3],n,c1,c2,c3,c4,i,j;
       printf("\nIntroduceti elementele Matricei cu 4 linii si 4 coloane: \n");
       int *mat;
       n=4;

       for (i=0; i<n; i++){
       for (j=0; j<n; j++){
           printf("a[%d][%d]=",i+1,j+1);
           scanf("%d",&a[i][j]);
           }
       }

       printf("\n Matri: \n");
       for (i=0; i<n; i++){
       for (j=0; j<n; j++){
           printf("%2d ",a[i][j]);
           }
       printf("\n");
       }


       for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
        b1[i][j]=a[i+1][j+1];;
           }
       printf("\n");
       }

       printf("\t Matri b1 : \n");
       for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
           printf("%2d ",b1[i][j]);
           }
       printf("\n");
       }

      for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
        b2[i][j]=a[i][j];
           }
       printf("\n");
       }

      printf("\tMatri b2: \n");
       for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
           printf("%2d ",b2[i][j]);
           }
       printf("\n");
       }

       for (i=0; i<n-2; i++){
       for (j=0; j<n-2; j++){
        b3[i][j]=a[i][j];
           }
           b3[2][0]=a[3][0];
           b3[2][1]=a[3][1];
           b3[2][2]=a[3][3];
           b3[1][2]=a[1][3];
           b3[0][2]=a[0][3];
       printf("\n");
       }

      printf("\tMatri b3 : \n");
       for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
           printf("%2d ",b3[i][j]);
           }
       printf("\n");
       }


     for (i=0; i<n-2; i++){
       for (j=0; j<n-2; j++){
        b4[i+1][j+1]=a[i+2][j+2];
           }
           b4[0][0]=a[0][0];
           b4[1][0]=a[2][0];
           b4[2][0]=a[3][0];
           b4[0][1]=a[0][2];
           b4[0][2]=a[0][3];
       printf("\n");
       }


       printf("\tMatri b4 : \n");
       for (i=0; i<n-1; i++){
       for (j=0; j<n-1; j++){
           printf("%2d ",b4[i][j]);
           }
       printf("\n\n");
       }

      c1=a[0][0]*( b1[0][0]*b1[1][1]*b1[2][2] + b1[1][0]*b1[2][1]*b1[0][2] + b1[2][0]*b1[0][1]*b1[1][2] - b1[0][2]*b1[1][1]*b1[2][0] - b1[1][2]*b1[2][1]*b1[0][0] - b1[1][0]*b1[0][1]*b1[2][2] );
       printf("\nComplementul algebric fata de elementul diagonalei principala a[1][1]: %d", c1);

       c2=a[1][1]*( b4[0][0]*b4[1][1]*b4[2][2] + b4[1][0]*b4[2][1]*b4[0][2] + b4[2][0]*b4[0][1]*b4[1][2] - b4[0][2]*b4[1][1]*b4[2][0] - b4[1][2]*b4[2][1]*b4[0][0] - b4[1][0]*b4[0][1]*b4[2][2] );
       printf("\nComplementul algebric fata de elementul diagonalei principala a[2][2]: %d", c2);

       c3=a[2][2]*( b3[0][0]*b3[1][1]*b3[2][2] + b3[1][0]*b3[2][1]*b3[0][2] + b3[2][0]*b3[0][1]*b3[1][2] - b3[0][2]*b3[1][1]*b3[2][0] - b3[1][2]*b3[2][1]*b3[0][0] - b3[1][0]*b3[0][1]*b3[2][2] );
       printf("\nComplementul algebric fata de elementul diagonalei principala a[3][3]: %d", c3);

       c4=a[3][3]*( b2[0][0]*b2[1][1]*b2[2][2] + b2[1][0]*b2[2][1]*b2[0][2] + b2[2][0]*b2[0][1]*b2[1][2] - b2[0][2]*b2[1][1]*b2[2][0] - b2[1][2]*b2[2][1]*b2[0][0] - b2[1][0]*b2[0][1]*b2[2][2] );
       printf("\nComplementul algebric fata de elementul diagonalei principala a[4][4]: %d", c4);

   getch();
   return 0;
}

with pointers, This is a program that calculates the algebraic complement
Sorry for my english

[Ancient Dragon]

why do you want to do that? I see no advantage of using pointers in that program, they could actually make it more difficult to read and comprehend the algorithm.

[dan1992]

i want just to see how the pointers will work in this program ,how to use pointers for this cind of problems

[DeanMSands3]

First, here's a tutorial on pointers:

/*
 ============================================================================
 Name        : PointersExplained1.c
 Author      : Dean M. Sands, III
 Version     : 0.1a
 Copyright   : I will set fire to the flamingos in your front yard.
 Description : A code explanation of pointers
 ============================================================================
 */

#include <malloc.h>
#include <stdio.h>
#include <conio.h>


int *i; //Define i as a pointer. Its present value is meaningless.
int j=0;  //Define j as an integer with a value of 0.

void pointerAsAReference(){
    printf("j is an integer that contains: %d\n", j);
    printf("i is an int pointer that contains: %d\n", i);
    printf("And no one cares about i right now since we haven't given it a useful value.\n");
    printf("That's right, i. No one likes you.\n");

    i=&j; //Assign the location of j into i;
    printf("We plugged j's location into i.\n");
    printf("j still contains: %d\n", j);
    printf("i now contains: %d\n", i);
    printf("OK, i...\nI apologize for the hurtful things I said earlier. You're truly useful now.\n");
    printf("...\n");
    printf("No, you can't borrow money.\n");

    *i=4; //Assign the number 4 to the space pointed to by i. j now contains 4.
    printf("Hey look what we can do! We assigned a value to the space pointed to by i\n");
    printf("i still contains the address: %d\n", i);
    printf("j now contains: %d\n", j);
    printf("You're so special, i!\n");
}

void pointerAsSingleElementArray(){

    i[0]=10; //Pointers can be used as variables.
    printf("Ooh! This is neat. Let's use i as a single element array!\n");
    printf("j now contains: %d\n", j);

}

void pointersToAllocatedBuffers(){
    int x; //loop variable
    //Allocate a buffer the size of j integers and plug its pointer into i.
    i=(int*)malloc(j*sizeof(int)); 
    printf("Now we're going to allocate a buffer %d bytes long.\nThis can be used as an int array that is %d elements long.\n", j*sizeof(int), j);
    printf("i now contains: %d\n", i);
    printf("j still contains: %d\n", j);
    printf("Feeling important yet, i?\n");

    //Fancy time!
    printf("Now we're doing something really super!\n");
    printf("We're going to plug cube numbers into i's array - just because we can!\n");
    for(x=0;x<j;x++){
        i[x]=x*x*x;
        printf("i[%d]=%d\n", x, i[x]);
    }
    //i now contains a pointer that can be used as an array.
    //Everything allocated during runtime needs to be freed during runtime.
    free(i);
}

int main(){
    pointerAsAReference();
    pointerAsSingleElementArray();
    pointersToAllocatedBuffers();
    return 0;
}

[DeanMSands3]

Now your new code:

/*
 ============================================================================
 Name        : Pointers.c
 Author      : dan1992
 Editor      : Dean M. Sands, III
 Version     : 0.2
 Copyright   : I will steal your lawn gnomes. And then the flamingos burn.
 Description : Algebraic Complement in C with Pointers
 ============================================================================
 */

#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <malloc.h>


int **allocateMatrix(unsigned int rows, unsigned int columns){
        int i, **matrix;
        //Malloc only allocates X number of bytes. It doesn't care that you want X number of INT pointers.
        //An INT pointer is a lot bigger than a byte.
        //So we have to specify:
        matrix=(int**)malloc(rows*sizeof(int*));        //Allocate pointers to rows
        printf("Matrix allocated!\n");
        if(matrix==NULL)
                return NULL;
        for(i=0;i<rows;i++){
                matrix[i]=(int*)malloc(columns*sizeof(int));    //Allocate each row
                printf("Row allocated!\n");
                if(matrix[i]==NULL){
                        return NULL;
                }
        }
        return matrix;
}

void deallocateMatrix(int **matrix, unsigned int rows){
        int i;
        for(i=0;i<rows;i++){
                free(matrix[i]);
        }
        free(matrix);
}



int main(){

        //int a[4][4],b4[3][3],b1[3][3],b2[3][3],b3[3][3],n,c1,c2,c3,c4,i,j;
        unsigned int n;
        int **a,**b4,**b1,**b2,**b3,c1,c2,c3,c4,i,j;
        n=4;
        //print("What size square matrix do you want? ");
        //scanf("%d", &n);
        a=allocateMatrix(n,n);
        if(a==NULL){
                printf("Could not allocate a.\n");
                return 0;
        }

        b1=allocateMatrix(n-1,n-1);
        if(b1==NULL){
                printf("Could not allocate b1.\n");
                return 0;
        }

        b2=allocateMatrix(n-1,n-1);
        if(b2==NULL){
                printf("Could not allocate b2.\n");
                return 0;
        }

        b3=allocateMatrix(n-1,n-1);
        if(b3==NULL){
                printf("Could not allocate b3.\n");
                return 0;
        }

        b4=allocateMatrix(n-1,n-1);
        if(b4==NULL){
                printf("Could not allocate b4.\n");
                return 0;
        }


        //printf("\nIntroduceti elementele Matricei cu 4 linii si 4 coloane: \n");
        printf("\nEnter the matrix elements with 4 rows and 4 columns: \n");

        for (i=0; i<n; i++){
                for (j=0; j<n; j++){
                        printf("a[%d][%d]=",i+1,j+1);
                        scanf("%d",&a[i][j]);
                }
        }

        printf("\n Matrix: \n");
        for (i=0; i<n; i++){
                for (j=0; j<n; j++){
                        printf("%2d ",a[i][j]);
                }
                printf("\n");
        }


        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        b1[i][j]=a[i+1][j+1];;
                }
                printf("\n");
        }

        printf("\t Matrix b1 : \n");
        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        printf("%2d ",b1[i][j]);
                }
                printf("\n");
        }

        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        b2[i][j]=a[i][j];
                }
                printf("\n");
        }

        printf("\tMatrix b2: \n");
        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        printf("%2d ",b2[i][j]);
                }
                printf("\n");
        }

        for (i=0; i<n-2; i++){
                for (j=0; j<n-2; j++){
                        b3[i][j]=a[i][j];
                }
                b3[2][0]=a[3][0];
                b3[2][1]=a[3][1];
                b3[2][2]=a[3][3];
                b3[1][2]=a[1][3];
                b3[0][2]=a[0][3];
                printf("\n");
        }

        printf("\tMatrix b3 : \n");
        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        printf("%2d ",b3[i][j]);
                }
                printf("\n");
        }


        for (i=0; i<n-2; i++){
                for (j=0; j<n-2; j++){
                        b4[i+1][j+1]=a[i+2][j+2];
                }
                b4[0][0]=a[0][0];
                b4[1][0]=a[2][0];
                b4[2][0]=a[3][0];
                b4[0][1]=a[0][2];
                b4[0][2]=a[0][3];
                printf("\n");
        }


        printf("\tMatrix b4 : \n");
        for (i=0; i<n-1; i++){
                for (j=0; j<n-1; j++){
                        printf("%2d ",b4[i][j]);
                }
                printf("\n\n");
        }

        c1=a[0][0]*( b1[0][0]*b1[1][1]*b1[2][2] + b1[1][0]*b1[2][1]*b1[0][2] + b1[2][0]*b1[0][1]*b1[1][2] - b1[0][2]*b1[1][1]*b1[2][0] - b1[1][2]*b1[2][1]*b1[0][0] - b1[1][0]*b1[0][1]*b1[2][2] );
        printf("\nComplementul algebric fata de elementul diagonalei principala a[1][1]: %d", c1);

        c2=a[1][1]*( b4[0][0]*b4[1][1]*b4[2][2] + b4[1][0]*b4[2][1]*b4[0][2] + b4[2][0]*b4[0][1]*b4[1][2] - b4[0][2]*b4[1][1]*b4[2][0] - b4[1][2]*b4[2][1]*b4[0][0] - b4[1][0]*b4[0][1]*b4[2][2] );
        printf("\nComplementul algebric fata de elementul diagonalei principala a[2][2]: %d", c2);

        c3=a[2][2]*( b3[0][0]*b3[1][1]*b3[2][2] + b3[1][0]*b3[2][1]*b3[0][2] + b3[2][0]*b3[0][1]*b3[1][2] - b3[0][2]*b3[1][1]*b3[2][0] - b3[1][2]*b3[2][1]*b3[0][0] - b3[1][0]*b3[0][1]*b3[2][2] );
        printf("\nComplementul algebric fata de elementul diagonalei principala a[3][3]: %d", c3);

        c4=a[3][3]*( b2[0][0]*b2[1][1]*b2[2][2] + b2[1][0]*b2[2][1]*b2[0][2] + b2[2][0]*b2[0][1]*b2[1][2] - b2[0][2]*b2[1][1]*b2[2][0] - b2[1][2]*b2[2][1]*b2[0][0] - b2[1][0]*b2[0][1]*b2[2][2] );
        printf("\nComplementul algebric fata de elementul diagonalei principala a[4][4]: %d", c4);

        deallocateMatrix(a,n);
        deallocateMatrix(b1,n-1);
        deallocateMatrix(b2,n-1);
        deallocateMatrix(b3,n-1);
        deallocateMatrix(b4,n-1);
        getch();
        return 0;
}

[dan1992]

Thank you so much I even understand how it works :D:D