1034.py

'''
Given a 2-dimensional grid of integers, each value in the grid represents the color of the grid square at that location.

Two squares belong to the same connected component if and only if they have the same color and are next to each other in any of the 4 directions.

The border of a connected component is all the squares in the connected component that are either 4-directionally adjacent to a square not in the component, or on the boundary of the grid (the first or last row or column).

Given a square at location (r0, c0) in the grid and a color, color the border of the connected component of that square with the given color, and return the final grid.

Example 1:

Input: grid = [[1,1],[1,2]], r0 = 0, c0 = 0, color = 3
Output: [[3, 3], [3, 2]]
Example 2:

Input: grid = [[1,2,2],[2,3,2]], r0 = 0, c0 = 1, color = 3
Output: [[1, 3, 3], [2, 3, 3]]
Example 3:

Input: grid = [[1,1,1],[1,1,1],[1,1,1]], r0 = 1, c0 = 1, color = 2
Output: [[2, 2, 2], [2, 1, 2], [2, 2, 2]]
 

Note:

1 <= grid.length <= 50
1 <= grid[0].length <= 50
1 <= grid[i][j] <= 1000
0 <= r0 < grid.length
0 <= c0 < grid[0].length
1 <= color <= 1000
'''

class Solution(object):
    def colorBorder(self, grid, r0, c0, color):
        """
        :type grid: List[List[int]]
        :type r0: int
        :type c0: int
        :type color: int
        :rtype: List[List[int]]
        """
        if not grid:
            return grid
        visited, border = [], []
        m, n = len(grid), len(grid[0])
        
        def dfs(r, c):
            if r < 0 or c < 0 or r >= m or c >= n or grid[r][c] != grid[r0][c0] or (r,c) in visited:
                return
            visited.append((r,c))
            
            # check if the current row, col index is edge of the matrix
            # if not then check adjacent cells doesnt have same value as grid[r0][c0] then add in border
            if (r == 0 or c == 0 or r == m-1 or c == n-1 or 
                (r+1 < m and grid[r+1][c] != grid[r0][c0]) or
                (r-1 >= 0 and grid[r-1][c] != grid[r0][c0]) or
                (c+1 < n and grid[r][c+1] != grid[r0][c0]) or
                (c-1 >= 0 and grid[r][c-1] != grid[r0][c0])):
                    border.append((r,c))
            dfs(r-1, c)
            dfs(r+1, c)
            dfs(r, c-1)
            dfs(r, c+1)
            
        dfs(r0, c0)
        for (x, y) in border:
            grid[x][y] = color
        return grid