HackerRank_HexagonalGrid_C#

//Solution to https://www.hackerrank.com/challenges/hexagonal-grid/problem

using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) {
        int T = Convert.ToInt32(Console.ReadLine());
        for(int i = 0; i < T; i++){
            int N = Convert.ToInt32(Console.ReadLine());
            string a = Console.ReadLine();
            string b = Console.ReadLine();
            int[] pos = new int[a.Length];
            for(int j = 0; j < a.Length; j++){
                pos[j] = a[j] == '1' ? 1 : 0;
            }
            int result = IsFillPossible(0, 0, a, b, pos);
            Console.WriteLine(result == 1 ? "YES" : "NO");
        }
    }
    
    public static int IsFillPossible(int startA, int startB, string a, string b, int[] pos){
        
        if(startB >= b.Length){
            for(int i = 0; i < pos.Length; i++){
                if(pos[i] == 1 || (pos[i] == 0 && (i + 1) < pos.Length && pos[++i] == 0))
                    continue;
                return 0;
            }
            return 1;
        }
        int n = 0;
        int ne = 0;
        int e = 0;
        if(b[startB] == '0'){
            if((startA <= startB) && (a[startB] == '0')){
                pos[startB] = 1;
                n = IsFillPossible(startB + 1, startB + 1, a, b, pos);
                pos[startB] = 0;
            }
            if(n != 1 && (startA <= startB) && (startB + 1 < a.Length) && (a[startB + 1] == '0')){
                pos[startB + 1] = 1;
                ne = IsFillPossible(startB + 2, startB + 1, a, b, pos);
                pos[startB + 1] = 0;
            }
            if(ne != 1 && ((startB + 1) < b.Length) && b[startB + 1] == '0'){
                e = IsFillPossible(startA, startB + 2, a, b, pos);
            }
            return n == 1 || ne == 1 || e == 1 ? 1 : 0;
        }
        else{
            return IsFillPossible(startA, startB + 1, a, b, pos);
        }
    }
}