How to use DFS on an array

Question

I have a 1 dimensional list of values, it looks like this "int[] values'". I beleive I have converted it to a 2d list like this :

for (int i = 0; i < 4; i++) {
    for (int j = 0; j < 4; j++) {
        board[i][j] = values[i * 4 + j];
    }
}

The board is the new 2 dimensional list of values. On the board there are numbers. A 0 means an empty space, a 1 is a green, a 2 is a blue, and a 3 is a red. How would I use depth first search to find a completed path of a certain color?

Answer 1

• Make a 2D array boolean[][] visited designating the points that you have visited; set all elements to false
• Go through each point in two nested loops
• For each point where visited[r][c] is false, go into a DFS which you can implement recursively
• Inside the recursive DFS call check if the point is your destination; if yes, return true
• If the point has the correct color, explore its neighbors (up to four) in four directions
• If a neighbor has the right color, mark it as visited, and make a recursive call
• If a recursive call returns true, return true
• Otherwise, continue exploring other neighbors
• Once you are done exploring neighbors, return false.