C program printing wrong output - c

Question

I am trying to create a program which prints a matrix of integers, but the output returns weird numbers before the actual matrix. There are no compiling errors.
This is what my code looks like: //ignore void function for now, focus on main function::
#include <stdio.h>
#include <stdlib.h>
//array[30][30] = 2D array of max 30 rows and 30 columns
//n = number of rows and columns
void printmatrix(int array[30][30], int n){
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
printf("%d", array[i][j]);
}
printf("\n");
}
return;
}
int main(){
int n;
scanf("%d", &n);
int ints2D[n][n];
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
scanf("%d", &ints2D[i][j]);
}
}
printmatrix(ints2D, n);
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
printf("%d ", ints2D[i][j]);
}
printf("\n");
}
return 0;
}
And this is my output (I only want the last three lines)
123
-514159984327663
-51415932632766-514159305
1 2 3
4 5 6
7 8 9

Answer 1

You are missing a space in "%d" in printmatrix, and, more importantly, it is not proper to pass an int [n][n] array for an int [30][30] parameter unless n is 30.
Change void printmatrix(int array[30][30], int n) to void printmatrix(int n, int array[n][n]), and change printmatrix(ints2D, n); to printmatrix(n, ints2D);. That makes the type of the argument you are passing match the type of the parameter.

Answer 2

In your function args you defined the array as fixed size ([30][30]) but you are passing a VLA ([3][3] in your example) which makes it find uninitialized memory and why you are seeing the strange numbers.
#Eric Postpischil answer is spot on. Another way to solve it: 2d arrays could be flatten into 1d. Here is a working code for you:
#include <stdio.h>
#include <stdlib.h>
//array[30][30] = 2D array of max 30 rows and 30 columns
//n = number of rows and columns
void printmatrix(int *array, int n){
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
printf("%d ", array[i * n + j]);
}
printf("\n");
}
return;
}
int main(){
int n;
scanf("%d", &n);
int ints2D[n * n];
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
scanf("%d", &ints2D[i * n + j]);
}
}
printmatrix(ints2D, n);
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
printf("%d ", ints2D[i * n + j]);
}
printf("\n");
}
return 0;
}