check column and row in sodoku- C programming - c

Question

I'm trying to check if number (from 1 to n)
appears more than once in
row or column in sodoku board
I wrote a code that goes over each row and column and checks the numbers between 1 to n (every time checking number at a time after finishing with row 0 (for example) goes to the next one (if it wasn't true in the row before)
my code is working just if there is a number
appearing more than once
in row 0 (if there is in other rows it returns nothing!)
and for the column it doesn't return any thing
this is a matrix that I use for the test (matrix with solution and I change numbers in rows or columns):
7 1 0 0 0 0 6 0 9
2 0 0 0 0 3 0 0 0
0 0 0 1 5 0 0 0 8
0 0 7 0 0 0 0 9 0
0 0 6 0 0 0 7 0 0
0 2 0 0 0 0 4 0 0
1 0 0 0 2 9 0 0 0
0 0 0 3 0 0 0 0 4
9 0 5 0 0 0 0 8 6
and this is my code:
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define MAX4USED 10
int n; //size of the sodoku board
bool CheckAppearingInRow(int matrix [n][n]) {
int used[MAX4USED] = {0};
int index = 1;
int row = 0;
while (index <= n) {
for(int j = 0; j < n; j++) {
if(matrix[row][j] == index ) {
used[index] +=1;
}
}
for(int i = 0; i <= n ; i++) {
if (used[i] > 1) {
return true;
}
used[i] = 0;
}
index += 1;
}
row += 1;
while (row < n) {
CheckAppearingInRow(matrix);
}
return false;
}
bool CheckAppearingInColumn(int matrix [n][n]) {
int used[MAX4USED] = {0};
int index = 1;
int col = 0;
while (index <= n) {
for(int i = 0; i < n; i++) {
if(matrix[i][col] == index ) {
used[index] +=1;
}
}
for(int i = 0; i <= n ; i++) {
if (used[i] > 1) {
return true;
}
used[i] = 0;
}
index += 1;
}
col += 1;
while(col < n){
CheckAppearingInColumn(matrix);
}
return false;
}
int main() {
printf("Please enter your sodoku dimension:");
scanf("%d", &n);
int a[n][n];
printf("\nInsert your sodoku board\n");
printf("Instruction: Enter 0 for blank\n");
for(int i=0; i<n; i++){
for(int j=0; j<n; j++) {
scanf("%d", &a[i][j]);
}
}
if (CheckAppearingInRow(a)== true || CheckAppearingInColumn(a) == true) {
printf("\nNo solution!\n");
}
return 0;
}