Printing a matrix and numbers under the second diagonal - c

Question

My task is to print out a matrix of integer numbers scanned from the keyboard, and then to print out the numbers under the second diagonal using separate functions. My code looks like this:
#include <stdio.h>
#include <stdlib.h>
//array[n][n] = 2D array of n rows and n columns
//n = number of rows and columns
void printmatrix(int n, int array[n][n]){
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
printf("%d ", array[i][j]);
}
printf("\n");
}
return;
}
void undersdiagonal(int n, int array[n][n]){
for(int i = 1; i < n; i++){
/**/
for(int j = 1; (j < n); j++){
printf("%d ", array[i][j]);
}
}
return;
}
int main(){
int n;
scanf("%d", &n);
int integermatrix[n][n];
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
scanf("%d", &integermatrix[i][j]);
}
}
printf("The entered matrix is:\n");
//calls first function to print matrix
printmatrix(n, integermatrix);
printf("Under the secondary diagonal:\n");
//calls second function to print numbers under main diagonal
undersdiagonal(n,integermatrix);
printf("\n");
return 0;
}
I can't figure out how to print out the numbers under the second main diagonal from the function
void undersdiagonal(int n, int array[n][n]).
My input looks like this:
3
1
2
3
4
5
6
7
8
9
And the output looks like this:
The entered matrix is:
1 2 3
4 5 6
7 8 9
Under the secondary diagonal:
5 6 8 9
But I want the output to be:
The entered matrix is:
1 2 3
4 5 6
7 8 9
Under the secondary diagonal:
6 8 9
What could I change in the 'for' loop within the 'for' loop in the function
void undersdiagonal(int n, int array[n][n])
?

Answer 1

The key is with the inner loop of undersdiagonal:
As currently written, for(int j = 1; (j < n); j++){ starts with the second column (column 1) every single time. It needs to start on a different column for each row.
For a 3×3 matrix, the second row (row 1) will begin on the last column (column 2). For a 4×4 matrix, the second row (row 1) will begin on the last column (column 3)... So there is a direct relationship between the starting column (j) and the matrix size: n.
Every time the row number goes up one, the starting column goes down one. So there is an inverse relationship between the starting column (j) and the row: - i.
Take those two pieces together and you have int j = n - i;