"""
Candy Crush:

This question is about implementing a basic elimination algorithm for Candy Crush:
Given a 2D integer array board representing the grid of candy, different positive integers board[i][j] represent different types of candies.
A value of board[i][j] = 0 represents that the cell at position (i, j) is empty.
The given board represents the state of the game following the player's move.

https://leetcode.com/problems/candy-crush/
"""


from typing import List


class Solution:

    # 1. Check for vertical match
    # 2. Check for horizontal match
    # 3. Gravity
    # 4. repeat till board is clean
    # cells to be crushed will be marked as negative
    def candyCrush(self, board: List[List[int]]):

        h = len(board)
        w = len(board[0])

        toBeCrushed = False

        #  1. Check for vertical match then
        # negate the found (three cells)
        # Note: (don't check the last two as they'll already have been checked)
        for x in range(h-2):
            for y in range(w):

                # check a cell and the two below it then
                # if they are equal, mark them (negate their values)
                if abs(board[x][y]) == abs(board[x+1][y]) == abs(board[x+2][y]) != 0:
                    board[x][y] = board[x+1][y] = board[x+2][y] = - \
                        abs(board[x][y])
                    toBeCrushed = True

        # 2. Check for horizontal match (similar to above)
        for y in range(w-2):
            for x in range(h):

                # check a cell and the two to its right
                # if they are equal, mark them
                if abs(board[x][y]) == abs(board[x][y+1]) == abs(board[x][y+2]) != 0:
                    board[x][y] = board[x][y+1] = board[x][y+2] = - \
                        abs(board[x][y])
                    toBeCrushed = True

        # 3. Gravity
        # iterate through each column, then for each column,
        # move positive values to the bottom then set the rest to 0.
        if toBeCrushed:  # not needed but speeds it up

            # # find negative values then, replace it with the ones above it using two pointers
            # it's easier to iterate from the bottom
            for y in range(w):

                # will stick on negative values till they are replaced
                anchor = h - 1  # starts off at the bottom

                for x in reversed(range(h)):

                    # Replacing the negative values:
                    # check if positive, if positive,
                    #   we replace the last anchored cell[anchor][y] with the current cell([x],[y])
                    #   then we move the anchor up
                    # (skip this on -ve values, wait till we hit a +ve value to replace it)
                    if board[x][y] > 0:
                        # FYI, the first cells, if possitive will be replaced by themselves
                        board[anchor][y] = board[x][y]
                        anchor -= 1  # move anchor up

                # deal with where the anchor last stuck,
                # all the values of cells from the anchor upwards to be marked as 0
                while anchor >= 0:
                    board[anchor][y] = 0
                    anchor -= 1

        # Repeat till the board is clean
        if toBeCrushed:
            return self.candyCrush(board)
        else:
            return board


"""
Example:

Input:
board =
[[110,5,112,113,114],[210,211,5,213,214],[310,311,3,313,314],[410,411,412,5,414],[5,1,512,3,3],[610,4,1,613,614],[710,1,2,713,714],[810,1,2,1,1],[1,1,2,2,2],[4,1,4,4,1014]]

Output:
[[0,0,0,0,0],[0,0,0,0,0],[0,0,0,0,0],[110,0,0,0,114],[210,0,0,0,214],[310,0,0,113,314],[410,0,0,213,414],[610,211,112,313,614],[710,311,412,613,714],[810,411,512,713,1014]]
"""


"""
Full Question:

This question is about implementing a basic elimination algorithm for Candy Crush.

Given a 2D integer array board representing the grid of candy, different positive integers board[i][j] represent different types of candies. A value of board[i][j] = 0 represents that the cell at position (i, j) is empty. The given board represents the state of the game following the player's move. Now, you need to restore the board to a stable state by crushing candies according to the following rules:

If three or more candies of the same type are adjacent vertically or horizontally, "crush" them all at the same time - these positions become empty.
After crushing all candies simultaneously, if an empty space on the board has candies on top of itself, then these candies will drop until they hit a candy or bottom at the same time. (No new candies will drop outside the top boundary.)
After the above steps, there may exist more candies that can be crushed. If so, you need to repeat the above steps.
If there does not exist more candies that can be crushed (ie. the board is stable), then return the current board.
You need to perform the above rules until the board becomes stable, then return the current board.

Note:

The length of board will be in the range [3, 50].
The length of board[i] will be in the range [3, 50].
Each board[i][j] will initially start as an integer in the range [1, 2000].
"""
