Print values of a 2D Dynamic matrix - c

Question

i cannot find solution how to solve this.
rows number is easy one. reading from keyboard and allocation but column number is different for each row.
lets assume user entered 2 rows after that user entered 3 column for row 0 and 10 column for row 1
and i dont know how to enter values for these columns and print them. because every column has different length. unfortunately != NULL not working
int** ptr; int rows, columns;
printf("enter number of rows..\n");
scanf("%d", &rows);
ptr = (int**)calloc(rows, sizeof(int*));
for (size_t i = 0; i < rows; i++) // allocation an array of integers for every row
{
printf("enter number of columns..\n");
scanf("%d", &columns);
ptr[i] = (int*)calloc(columns, sizeof(int));
}
for (size_t i = 0; i < rows; i++){
for (size_t j = 0; ptr[i][j] != NULL; j++)
ptr[i][j] = j;
}
for (size_t i = 0; i < rows; i++){
for (size_t j = 0; ptr[i][j] != NULL; j++)
printf("%d\n", ptr[i][j]);
}

Answer 1

Since C arrays don't have a final delimiter, then you need to store the length in an efficient way:
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
int main()
{
int** ptr; int rows, columns;
printf("enter number of rows..\n");
scanf("%d", &rows);
ptr = (int**)calloc(rows, sizeof(int*));
for (size_t i = 0; i < rows; i++) // allocation an array of integers for every row
{
printf("enter number of columns..\n");
scanf("%d", &columns);
ptr[i] = (int*)calloc(columns+1, sizeof(int)); // Last pos will save the size
// We need to track the columns since C arrays do not have a final delimiter
ptr[i][columns] = INT_MIN; // It could also be INT_MAX depending on our needs
}
for (size_t i = 0; i < rows; i++){
for (size_t j = 0; ptr[i][j] != INT_MIN; j++)
ptr[i][j] = j;
}
for (size_t i = 0; i < rows; i++)
{
printf("Line %li\n", i);
for (size_t j = 0; ptr[i][j] != INT_MIN; j++)
{
printf(" Column %li: ", j);
printf("%d\n", ptr[i][j]);
}
}
return 0;
}