DFS.java

import java.util.Arrays;

public class DFS {
    static char[][] grid;
    static int counter = 0;
    static boolean inside(int row, int col) {
        return row >= 0 && col >= 0 && row < 6 && col < 6;
    }
    static void dfs(int row, int col) {
        char color = grid[row][col];
        grid[row][col] = '6';
        counter++;
        int dr[] = {-1, 1, 0, 0};
        int dc[] = {0, 0, -1, 1};
        for(int d = 0; d < 4; d++){
            int newRow = dr[d] + row;
            int newCol = dc[d] + col;
            if(inside(newRow, newCol) && grid[newRow][newCol] == color){
                dfs(newRow, newCol);
            }
        }
    }
    public static void main(String[] args) {
        grid = new char[][]{
                {'1', '1', '1', '1', '1'},
                {'1', '2', '3', '3', '2'},
                {'3', '3', '3', '3', '5'},
                {'5', '2', '4', '3', '4'},
                {'4', '3', '1', '3', '4'},
                {'5', '3', '5', '3', '2'},
        };
        int row = 2, col = 2;
        dfs(row, col);
        for(char[] r: grid)
            System.out.println(Arrays.toString(r));
        System.out.println("Changed " + counter + " threes");
    }
}