Trying to find duplicates in a Struct Array in C - c

Question

I've attempted to find if the user has inputted a product id value that's a duplicate and if so, it just tells them that it's a duplicate value and then returns to the menu in my switch statement.
The actual result i get, is that after "productsfilled == 0", it won't utilise the For Loops to check for the duplicates and productsfilled will remain at 1. I've looked online and this way of finding duplicates tends to work and i have used it previously in my code, so I don't think that could be the issue.
Here's my code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <conio.h>
int productsfilled;
struct ProductData{
int product_id;
char product_name[120];
int price;
};
int quiz_5(){
char ch;
int size, input = 0;
struct ProductData products[20];
while(1){
printf("\nWelcome To The Super Mall's Product List. Please Select An Option:\n1. Add Product\n2. Display Product\n3. Delete Product\n");
fflush(stdin);
switch(getchar()){
case '1':
printf("\nPlease Enter Product ID:");
scanf("%d",&products[productsfilled].product_id);
printf("\nPlease Enter Product Name:");
scanf("%s",&products[productsfilled].product_name);
printf("\nPlease Enter Product Price:");
scanf("%d",&products[productsfilled].price);
printf("Productsfilled: %d",productsfilled);
if(productsfilled == 0){
productsfilled = 1;
break;
}
for(int i = 0; i < productsfilled;i++){
for (int j = i + 1; j < productsfilled;j++){
if(products[i].product_id == products[j].product_id){
printf("\nPlease Use Different Product ID");
break;
}else{
printf("test");
productsfilled += 1;
break;
}
}
}
break;
case '2':
while(1){
for(int i = 0;i < productsfilled;i++){
printf("Product ID: %d Product Name: %s Product Price: %d\n",products[i].product_id,products[i].product_name,products[i].price);
}
printf("Please Press Enter To Continue");
fflush(stdin);
if(getchar() == '\n'){
break;
}
}
case '3':
break;
case '\n':
break;
default:
printf("Please Select An Option:\n1. Add Product\n2. Display Product\n3. Delete Product: ");
}
}
}
int main() {
int input = 1;
printf("Welcome to my assignment. Which quiz do you want to run (please input the number of the quiz e.g. for quiz 1, type 1): \n-Quiz 1\n-Quiz 2\n-Quiz 3\n-Quiz 4\n-Quiz 5\n-Quiz 6\n-Quiz 7\n");
while(input == 1){
fflush(stdin);
switch(getchar()){
case '5':
quiz_5();
break;
case '\n':
printf("Welcome to my assignment. Which quiz do you want to run (please input the number of the quiz e.g. for quiz 1, type 1): \n-Quiz 1\n-Quiz 2\n-Quiz 3\n-Quiz 4\n-Quiz 5\n-Quiz 6\n-Quiz 7\n");
getchar();
default:
printf("Invalid Input\n");
} }
return 0;
}

Answer 1

The problem is that you don't increment productsfilled before you enter the loop...therefore, productsfilled is always 1 less than the actual length of your array which means that you don't compare all elements in the array.
Try your program on 2 inputs, both with the same ID. You'll see that you don't compare anything.

Answer 2

You are wrong when using scanf for string input:
scanf("%s",&products[productsfilled].product_name);
You should not use &, you should use as below:
scanf("%119s",products[productsfilled].product_name);
OT, in main function:
switch(getchar()){
case '5':
...
Because getchar() will return int value, so if you want to access to quiz_5, you have to type 35 (ANSCI code) instead of type 5 when you run your program.
char a = '5';
similar to:
int a = 35;