How can I pass a matrix to a double pointer function?

Question

I have a problem with this program, the program must simply output the minimum value contained in a matrix, this must be done by the function that has as parameter the double pointer (**A) that would be the array , the problem is that after inserting the items , the program finishes and returns nothing.

(I don’t even appear written outuput instruction )

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

int minium_matrix_value(int **A, int rows, int columns) {
    int min=A[0][0];
    
    for(int i=0;i<rows;i++){
        for(int j=0;j<columns;j++)
           
            if(A[i][j]<min)
                min=A[i][j];
    }
    return min;
}

int main(){
    
   int** A;
   int i, j;
   int result;
   int sizer=100, sizec=100;
 
   A = (int**)calloc(sizer,sizeof(int*));
   A = (int**)calloc(sizec,sizeof(int*));
   printf("insert rows size");
   scanf("%d",&sizer);
   printf("insert columns size");
   scanf("%d",&sizec);

   printf("insert matrix elements");
   for( i=0; i < sizer; i++ )
       for( j=0; j < sizec; j++ ) {
           scanf("%d",((A+i)+j));
       }
    
    result=minium_matrix_value(A,sizer,sizec);
    printf("the minium elements is: %d",result);
   
    return 0;

}

Answer 1

• You only allocated arrays to store pointers to rows. You have to allocate arrays for storing values of each rows.
• Using the value of sizer should be after reading value into that/

     // move this after scanf()
     // A = (int**)calloc(sizer,sizeof(int*));
     // remove this, or memory leak occur
     // A = (int**)calloc(sizec,sizeof(int*));
     printf("insert rows size");
     scanf("%d",&sizer);
     printf("insert columns size");
     scanf("%d",&sizec);

     // move here
     A = calloc(sizer,sizeof(int*));

     printf("insert matrix elements");
     for( i=0; i < sizer; i++ ) { // add { to do multiple things
       A[i] = calloc(sizec,sizeof(int)); // allocate row array
       for( j=0; j < sizec; j++ ) {
        //scanf("%d",((A+i)+j));
        scanf("%d",&A[i][j]); // use array style, which should be easier to understand
       }
     } // add } to do multiple things

Also note that:

• scanf("%d",((A+i)+j)); is wrong and it should be scanf("%d",(*(A+i)+j)); if you hate [] operator.
• Casting result of malloc() family is discouraged in C.