use to matrix and double pointer - c

Question

The size of the square matrix is entered as standard input (the range of input values is 2 to 10). Create a program that prints the unit matrix of the input size.
The unit matrix is a matrix whose diagonal from the top left to the bottom right (main diagonal) is 1 and all others are zero.
ex) input: 5
result :
1 0 0 0 0\n
0 1 0 0 0\n
0 0 1 0 0\n
0 0 0 1 0\n
0 0 0 0 1\n
my code:
int main(){
int n;
scanf("%d", &n);
int **matrix = malloc(sizeof(int *) * n);
for (int i = 0; i < n; i++)
{
matrix[i] = malloc(sizeof(int) * n);
memset(matrix[i], 0, sizeof(int) * n);
}
for (int i = 0; i < n; i++)
{
matrix[i][i] = 1;
printf("%d ", matrix[i][i]);
}
printf("\n");
for (int i = 0; i < n; i++)
{
free(matrix[i]);
}
free(matrix);
return 0;
}
.. what 's the error?

Answer 1

You need a double loop to print the output:
for (int i = 0; i < n; i++)
{
matrix[i][i] = 1; // set identity
}
for (int j=0; j<n; j++)
{
for (int i = 0; i < n; i++)
{
printf("%d ", matrix[j][i]);
}
printf("\n");
}

Answer 2

One error is to think yo need a data strucure to print the output requested.
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
int n;
if (scanf("%d", &n) != 1 || n < 2 || 10 < n) {
perror("Input error!\n\n");
return EXIT_FAILURE;
}
for (int i = 0; i < n; ++i) {
for (int k = 0; k < n; ++k)
printf(i == k ? "1 " : "0 ");
putchar('\n');
}
}