12884 - Patruto and Spongebob run away

#include <stdio.h>

int arr[1000][1000];
int main(){
    int n;
    scanf("%d", &n);
    int len = 2*n;
    // n = 3 6x6 grid
    // 1  2  3  4  5  6
    // 20 21 22 23 24 7
    // 19 32 33 34 25 8
    // 18 31 36 35 26 9
    // 17 30 29 28 27 10
    // 16 15 14 13 12 11
    int m = 1; //filling the array
    //q is the loop how many time he goes from outer to inner and repeats
    //so, 1 ~ n, means that patrick goes to outer from inner n times
    for(int q = 1; q <= n; q++){
        //right
        for(int i = q; i <= q; i++){
            for(int j = q; j <= len - q; j++){
                arr[i][j] = m++;
                //1 2 3 4 5
            }
        }
        // down
        for(int j = len + 1 - q; j <= len + 1 - q; j++){
            for(int i = q; i <=len - q; i++){
                arr[i][j] = m++;
                //6 7 8 9 10
            }
        }
        //left
        for(int i = len + 1 - q; i <= len + 1 - q; i++){
            for(int j = len + 1 - q; j >= q + 1; j--){
                arr[i][j] = m++;
                //11 12 13 14 15
            }
        }
        //top
        for(int j = q; j <= q; j++){
            for(int i = len + 1 - q; i >= q+1; i--){
                arr[i][j] = m++;
                //16 17 18 19 20
            }
        }

    }
    int i, j;
    for( i = 1; i <=len ; i++){
        for(j = 1; j <= len- 1; j++){
            printf("%d ", arr[i][j]);
        }
        printf("%d\n", arr[i][j]);
    }
    return 0;
}
//note : right
//i does not change, but j keeps incrementing by 1
//i and j always start from q as when q increase i does not start at the same tile
//and start depends on q
//repeat the step for everything, find the relation between q and len and i or j
//remember to change the loop for downward because this time j does not change, but i keeps incrementing by 1