C program to fill an array

The problem is to fill the array like this if n = 4

output of my code:

1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4

desired output:

1 2 3 4
2 3 4 3
3 4 3 2
4 3 2 1

My friend said this problem is easy but I can’t figure it out, please help. The code I wrote:

#include <stdio.h>
main()
{
    int i,j,n;
    int a[100][100];
    printf("Enter the value of n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++)
        {
            a[i][j]=j;      
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++)
        { 
            printf("%d ",a[i][j]);
        }        
        printf("\n");
    }
}

>Solution :

You always start counting from 1 upwards, but you don’t have a loop where you count backwards, like in the desired output.

I would recommend to use two for loops, one which counts upwards and one downwards. Also you don’t need an array, you can print out the numbers directly:

main()
{
    int i,j,n;
    printf("Enter the value of n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        for(j = i; j < n; j++)
        {
            printf("%d ", j);     
        }
        for(j = n; j > n-i; j--)
        {
            printf("%d ", j); 
        }
        printf("\n");
    }
}