How to transpose matrix with malloc and print it - c

Question

I want my code to scan value of rows and cols and then to print the matrix (I don't care from the values in the matrix) and to print the transpose matrix.
What is my problem with mine code?
the code :
#include <stdio.h>
#include <string.h>
void main()
{
int rows1, colums1, i, j;
int**matrix1, **transpose_matrix1;
printf_s("enter rows and colums\n");
scanf_s("%d%d", &rows1, &colums1);
matrix1 = malloc(sizeof(int*)*rows1);
for (i = 0; i < rows1; i++)
matrix1[i] = malloc(sizeof(int)*colums1);
for (i = 0; i < rows1; i++)
for (j = 0; j < colums1; j++)
matrix1[i][j] = i+j;
puts("matrix: ");
for (i = 0; i < rows1; i++)
{
for (j = 0; j < colums1; j++)
{
printf_s("%d ", matrix1[i][j]);
}
printf_s("\n");
}
transpose_matrix1 = malloc(sizeof(int*)*colums1);
for (i = 0; i < colums1; i++)
transpose_matrix1[i] = malloc(sizeof(int)*rows1);
for (i = 0; i < rows1; i++)
for (j = 0; j < colums1; j++)
transpose_matrix1[j][i] = matrix1[i][j];
puts("transpose matrix:");
for (i = 0; i < rows1; i++)
{
for (j = 0; j < colums1; j++)
{
printf_s("%d ", transpose_matrix1[i][j]);
}
printf_s("\n");
}
}
Input:
2 3
0 1 2
1 2 3
Output:
enter rows and colums
matrix:
transposematrix:
0 1 -33686019
1 2 -33686019

Answer 1

When you initialize the transpose matrix you do it like
transpose_matrix1[j][i] = matrix1[i][j];
Note the order in which you use j and i in transpose_matrix1[j][i].
Then when you print you use transpose_matrix1[i][j]. Note that the order of j and i have changed, even though the looping around both are the same. You need to use the same order for j and i in both loops.

Answer 2

You have confused yourself a little with what is a colum and what is a row
here is a fixed version:
void print_matrix(int ** matrix, int rows, int colums){
int i,j;
for (i = 0; i < rows; i++)
{
for (j = 0; j < colums; j++)
{
printf("%d ", matrix[i][j]);
}
printf("\n");
}
}
int main()
{
int transpose_rows1, transpose_colums1, rows1, colums1, i, j;
int**matrix1, **transpose_matrix1;
printf("enter rows and colums\n");
scanf("%d%d", &rows1, &colums1);
matrix1 = (int**)malloc(sizeof(int*)*rows1);
for (i = 0; i < rows1; i++)
matrix1[i] = (int*)malloc(sizeof(int)*colums1);
for (i = 0; i < rows1; i++)
for (j = 0; j < colums1; j++)
matrix1[i][j] = i+j;
puts("matrix: ");
print_matrix(matrix1, rows1, colums1);
transpose_rows1 = colums1;
transpose_colums1 = rows1;
transpose_matrix1 = (malloc(sizeof(int*) * transpose_rows1));
for (i = 0; i < transpose_rows1; i++)
transpose_matrix1[i] = (malloc(sizeof(int) * transpose_colums1));
for (i = 0; i < rows1; i++)
for (j = 0; j < colums1; j++)
transpose_matrix1[j][i] = matrix1[i][j];
puts("transpose matrix:");
print_matrix(transpose_matrix1, transpose_rows1, transpose_colums1);
return 0;
}
In order to not confuse yourself in the future, try to use function and names with the exact meaning.
It is easier to create a function to print the array than to write the code twice and then thinking twice about what is the row now and what is the column.
And also, it makes it easier if the variable name colums1 is always a column of a matrix, not a column on one and a row on the other, so just create a new variable for the second array column and row with the correct data.

Answer 3

In a transponsed matrix, the number of rows is the number of columns of the normal matrix and the number of columns is equal to the number of rows of the normal matrix. Therefore, i should go from 0 to columns1 and j from 0 to rows1:
for (i = 0; i < colums1; i++)
for (j = 0; j < rows1; j++)
transpose_matrix1[i][j] = matrix1[j][i];
puts("transpose matrix:");
for (i = 0; i < colums1; i++)
{
for (j = 0; j < rows1; j++)
{
printf("%d ", transpose_matrix1[i][j]);
}
printf("\n");
}