Check some

public static boolean checkDuplicateWithinK(int[][] mat, int k){
    class Cell{
        int row;
        int col;
        public Cell(int r, int c){
            this.row = r;
            this.col = c;
        }
    }
    int n = mat.length;
    int m = mat[0].length;
    k = Math.min(k, n*m);
    //map from distance to cell postions of the matrix
    Map<Integer, Set<Cell>> map = new HashMap<Integer, Set<Cell>>();
    for(int i = 0; i < n; i++){
        for(int j = 0; j < m; j++){
            if(map.containsKey(mat[i][j])){
                for(Cell c : map.get(mat[i][j])){
                    int Dist = Math.abs(i - c.row)+Math.abs(j - c.col);
                    if(Dist <= k){
                        return true;
                    }
                    if(i - c.row > k){
                        map.remove(c);
                    }
                }
                map.get(mat[i][j]).add(new Cell(i, j));
            }
            else{
                map.put(mat[i][j], new HashSet<Cell>());
                map.get(mat[i][j]).add(new Cell(i, j));
            }
        }
    }
    return false;
}

public boolean checkDuplicatesWithinK(int[][] matrix, int k) {
        //convert matrix to an array
        int[] arr = Arrays.stream(matrix)
                .flatMapToInt(Arrays::stream)
                .toArray();


        // Creates an empty hashset
        HashSet<Integer> set = new HashSet<>();

        // Traverse the input array
        for (int i = 0; i < arr.length; i++) {
            // If already present n hash, then we found
            // a duplicate within k distance
            if (set.contains(arr[i]))
                return true;

            // Add this item to hashset
            set.add(arr[i]);

            // Remove the k+1 distant item
            if (i >= k)
                set.remove(arr[i - k]);
        }

    
        return false;
    }