I get segmentation error

This program asks user to enter numbers between 1 and 100. After i run it i get segmentation error. The program doesnt repeat number twice. Can someone help me.

Code:

#include<stdio.h>
#define SIZE 20
int main(void)
{
 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;


  printf("Enter 20 numbers between 1 and 100\n");
  scanf("%d",&a[i]);

//this is how to accept multiple numbers
  for (int i = 0; i < 20;i++){
        scanf("%d",&x);
        a[i]=x;

        // this is to determine that numbers dont repeat
        if(i==0){
                a[i]=x;
                idx++;
        }
        else{
                for( int j=0; j<idx; j++){


                }

        }

        if(flag !=1){
                a[idx]=x;
                idx++;
        }

  printf("The no duplicate values are:\n");
  printf("\n%d",x);
 }



return 0;
}

Code:

scanf("%d",&a[i]);

You need to initialize i before you can use it. You initialize it after this point in your for loop.

The error is probably coming from this though:

Code:

for (int i = 0; i < 20;i++){

you already declared i as an int before the for loop, this should just be i = 0 (actually it shouldn't since you've already taken one value for your a array )

You also declare j twice.

can you specify, what you mean?

Code:

 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;


  printf("Enter 20 numbers between 1 and 100\n");
  scanf("%d",&a[i]);

You have not given a value to i, so where is scanf going to place the inputted value? &a[i] needs a value for i.

Code:

for (int i = 0; i < 20;i++){
...
for( int j=0; j<idx; j++){

You have already declared these variables at the beginning:

Code:

 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;

you don't need to declare them again, just give them values, i.e. i = 0, j = 0

Like this... i still keep getting the segmentation error

Code:

#include<stdio.h>
#define SIZE 20

int main(void)
{
 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;


  printf("Enter 20 numbers between 10 and 100\n");
  scanf("%d",&a[i]);

//this is how to accept multiple numbers
  for (i = 0; i < 20;i++){
        scanf("%d",&x);
        a[i]=x;

        // this is to determine that numbers dont repeat
        if(i==0){
                a[i]=x;
                idx++;
        }
        else{
                for( j=0; j<idx; j++){


                }

        }

        if (a[j]==x){
                flag=1;
        }

        if(flag !=1){
                a[idx]=x;
                idx++;
        }


  printf("The no duplicate values are:\n");
  printf("\n%d",x);
 }



return 0;
}

Code:

 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;


  printf("Enter 20 numbers between 10 and 100\n");
  scanf("%d",&a[i]);

&a[i] is telling scanf to place the input at the address of the 'i'th term in the 'a' array. Again, you have not supplied a value for i...so it doesn't know what part of the array you want to use. Try:

Code:

 int a[SIZE];
 int i;
 int x;
 int j;
 int flag;
 int idx=0;


  printf("Enter 20 numbers between 10 and 100\n");
  scanf("%d",&a[0]);

//this is how to accept multiple numbers
//i = 1 because a[0] has already been filled
  for (i = 1; i < 20;i++){

I tried everything you told me, it still gives me segmentation error.

Isn't the problem that you shouldn't use the addressof operator on the array?

what do you mean?

Nevermind, I think I'm confusing things here.

Warning 3 warning C6001: Using uninitialized memory 'i': Lines: 6, 7, 8, 9, 10, 11, 14, 15 15
Warning 4 warning C6001: Using uninitialized memory 'j': Lines: 6, 7, 8, 9, 10, 11, 14, 15, 18, 19, 20, 23, 24, 25, 35 35
Warning 5 warning C6001: Using uninitialized memory 'flag': Lines: 6, 7, 8, 9, 10, 11, 14, 15, 18, 19, 20, 23, 24, 25, 35, 39 39
Warning 6 warning C4700: uninitialized local variable 'i' used 15

What this is saying is that you are using a lot of uninitialized variables.