func rSearch(matrix *[][]int32, r, c, rows, cols int32) int32 {
    sum := int32(1)
    (*matrix)[r][c] = int32(2) // mark cell as visited
    for i := int32(-1); i <= 1; i++ {
        for j := int32(-1); j <= 1; j++ {
            if (i == 0 && j == 0) ||
            r + i < 0 || r + i >= rows ||
            c + j < 0 || c + j >= cols {
                continue
            }
            if (*matrix)[r+i][c+j] == 1 {
                sum += rSearch(matrix, r + i, c + j, rows, cols)
            }
        }
    }
    return sum
}

func connectedCell(matrix [][]int32) int32 {
    // - iterate over matrix left to right top to bottom
    // - when finding a cell, recursively explore the unvisited neighbors
    rows := int32(len(matrix))
    cols := int32(len(matrix[0]))
    var mSize int32
    for r := int32(0); r < rows; r++ {
        for c := int32(0); c < cols; c++ {
            if matrix[r][c] == 1 {
                size := rSearch(&matrix, r, c, rows, cols)
                if size > mSize {
                    mSize = size
                }
            }
        }
    }
    return mSize
}