Sort a matrix row wise (c programming) - c

Question

I wrote this code for sorting an nxn matrix: odd rows in descending order, double rows in ascending order, but it doesn't pass the compiler stage.
What did I do wrong?
It mostly tells me this: assignment to 'int' from 'int *' makes integer from pointer without a cast (how can I solve this problem)?
#include <stdio.h>
#include <stdlib.h>
int comp_a(int a, int b) {
if (a < b) {
return 1;
} else {
return 0;
}
}
int comp_d(int a, int b) {
if (a > b) {
return 1;
} else {
return 0;
}
}
void sort(int a[], int n, int (*comp)(int, int)) {
int t;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n - 1; j++) {
if (comp(a[j], a[j + 1]) == 0) {
t = a[j];
a[j] = a[j + 1];
a[j + 1] = t;
}
}
}
}
int main() {
int n;
printf("Enter the dimension of matrix(n): ");
scanf("%d", &n);
int *mat = (int*)calloc(n, sizeof(int));
for (int i = 0; i < n; i++) {
mat[i] = (int*)calloc(n, sizeof(int));
}
for (int i = 0; i < n; i++) {
printf("Enter row [%d]: ", i);
for (int j = 0; j < n; j++) {
scanf("%d", &mat[i][j]);
}
}
for (int i = 0; i < n; i++) {
if (i%2 == 0) {
sort(mat[i], n, &comp_a);
} else {
sort(mat[i], n, &comp_d);
}
}
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
printf("%d ", mat[i][j]);
}
printf("\n");
}
return 0;
}

Answer 1

You should change your matrix allocation to this:
int **mat = (int**)calloc(n, sizeof(int*)); // (1)
for(int i = 0; i < n; i++) {
mat[i] = (int*)calloc(n, sizeof(int)); // (2)
}
(1): Declaring an array of pointers of size n x int*.
(2): Where each pointer in this array points to an array of integers of size n x int.

Answer 2

I changed your matrix allocation
int *mat = (int*)calloc(n, sizeof(int));
for(int i = 0; i < n; i++) {
mat[i] = (int*)calloc(n, sizeof(int));
}
to
int mat[n][n];
I changed for loop of ordred
for(int i = 0; i < n; i++) {
for(int j = 0; j < n - 1; j++) {
if(comp(a[j], a[j + 1]) == 0)
because he take a lot of time (time of running) to
for(int i = 0; i < n; i++) {
for(int j = i+1; j < n; j++) {
if(comp(a[i], a[j]) == 0)
my code:
#include <stdio.h>
#include <stdlib.h>
int comp_a(int a, int b) {
if(a < b) {
return 1;
}
else {
return 0;
}
}
int comp_d(int a, int b) {
if(a > b) {
return 1;
}
else {
return 0;
}
}
void sort(int a[], int n, int (*comp)(int, int)) {
int t;
for(int i = 0; i < n; i++) {
for(int j = i+1; j < n; j++) {
if(comp(a[i], a[j]) == 0) {
t = a[j];
a[j] = a[i];
a[i] = t;
}
}
}
}
int main() {
int n;
do
{
printf("Enter the dimension of matrix(n): ");
scanf("%d", &n);
}while(n<1);
int mat[n][n];
for(int i = 0; i < n; i++) {
printf("Enter row [%d]: ", i);
for(int j = 0; j < n; j++) {
scanf("%d", &mat[i][j]);
}
}
for(int i = 0; i < n; i++) {
if(i%2 == 0) {
sort(mat[i], n, &comp_a);
}
else {
sort(mat[i], n, &comp_d);
}
}
for(int i = 0; i < n; i++) {
for(int j = 0; j < n; j++) {
printf("%d ", mat[i][j]);
}
printf("\n");
}
return 0;
}