Can anyone help me below mentioned code showing wrong result for last 3 test case.

import java.io.; import java.math.; import java.security.; import java.text.; import java.util.; import java.util.concurrent.; import java.util.function.; import java.util.regex.; import java.util.stream.*; import static java.util.stream.Collectors.joining; import static java.util.stream.Collectors.toList;

// class Result {

public static HashMap<HashMap<Integer,Integer>,Integer> hm = new HashMap<>();
public static int grundy(int x,int y){
    HashMap<Integer,Integer> p = new HashMap<>();
    p.put(x,y);
    if(hm.containsKey(p)) return hm.get(p); 
    HashSet<Integer> set = new HashSet<>();
    if(x>=1 && y>=1 && x<=15 && y<=15){
        set.add(grundy(x-2, y+1));
        set.add(grundy(x-2, y-1));
        set.add(grundy(x+1, y-2));
        set.add(grundy(x-1, y-2));
    }
    int mex;
    for(int i = 0; ; i++)
    {
        if(set.contains(i)){
            continue;
        }
        mex = i;
        break;
    }
    // g = !g;
    hm.put(p, mex);
    return mex;

 }

public static String chessboardGame(int[][] coins) {
// Write your code here
    int xorsum = 0;
    for(int i = 0; i < coins.length; i++){
        int x = coins[i][0];
        int y = coins[i][1];

        // System.out.println("x="+x+"  y ="+y);

        int g = grundy(x, y);

        xorsum ^= g;
        // System.out.println(g);
    }
    // System.out.println(hm);
    return xorsum == 0?"Second":"First";

}

}

public class Solution { public static void main(String[] args) throws IOException { Scanner sc = new Scanner(System.in); int t = sc.nextInt(); while(t-->0){ int k = sc.nextInt(); int[][] arr = new int[k][2]; for(int i = 0 ; i < k; i++){ arr[i][0] = sc.nextInt(); arr[i][1] = sc.nextInt(); } String result = Result.chessboardGame(arr); System.out.println(result); } } }

Here is Chessboard game again! problem solution in Python Java C++ and c programming - https://programs.programmingoneonone.com/2021/07/hackerrank-chessboard-game-again-problem-solution.html

Too difficult for me

A good one . If You understand grandy theorem of game theory , then it is very easy for you to solve recursively .When our possible moves from a co-ordinate of chess-board has been given .We can compute grandy-value recursively using the help of memoization .

My full solution here https://github.com/joy-mollick/Game-Theory-Problems/blob/master/HackerRank-Chessboard%20Game%2C%20Again!.cpp

Here is the part of my code to compute grandy value of every co-ordinate by given input .

int sg(int x,int y)
{
    if((x==1&&y==1))
    {
        return 0;
/// (1,1) it is base case ,because from here there is no move,so grandy value of this state is zero
    }
    if(grandy_value[x][y]!=-1) /// if grandy value is already computed just return it , no need to calculate it
    {
        return grandy_value[x][y];
    }
    set<int>s;
    for(int i=0;i<4;i++)
    {
        int newx=x+dx[i];
        int newy=y+dy[i];
        if(newx>=1&&newy>=1&&newx<=15&&newy<=15)///if newx and newy is beyond (1,1) then this recursion will be recursively run ,there is no end .So (1,1) should be the terminal point
        {
            s.insert(sg(newx,newy));
        }
    }
    int mex=0;
    while(s.find(mex)!=s.end()) mex++;
    grandy_value[x][y]=mex;///assigning mex [not included minimum element in the set of grandy value of possible co-ordinates]
    return grandy_value[x][y];/// return grandy_value
}

What? A cell can contain more than one coin. Ok, when can not a player make a new move?