Is Candy Crush easy or hard?

Candy Crush is rated Medium because the logic is straightforward but the implementation requires careful handling of repeated board updates. Many candidates struggle with correctly marking candies and applying gravity without breaking overlapping matches.

Candy Crush Python/Java solution

Implement the mark-and-drop simulation: scan the board to mark sequences of three or more equal candies horizontally or vertically, negate their values to mark them, then compress each column downward and fill remaining cells with zeros. This logic translates directly to Python, Java, C++, Go, and TypeScript.

How to solve Candy Crush in O(n)?

Candy Crush cannot be solved in strict O(n) time for a general m x n board because each crush operation may cause cascading updates across rows and columns. The practical solution is a simulation that repeatedly scans the board and applies gravity, giving a time complexity around O(m*n*max(m,n)).

What is the best approach for Candy Crush?

The mark-and-drop simulation approach is the most reliable solution. First scan the grid to mark all candies that form horizontal or vertical groups of three or more, then apply gravity to drop remaining candies down each column. Repeat until no more groups exist. This approach runs in O(m*n*max(m,n)) time and uses O(1) extra space.

Is Candy Crush asked at Google/Amazon/Meta?

Grid simulation problems like Candy Crush appear in interviews at companies such as Amazon, Google, and Meta because they test careful implementation and edge-case handling. The question evaluates matrix traversal, state updates, and clean simulation logic.

What data structure is used in Candy Crush?

The main data structure is a 2D array (matrix) representing the game board. The algorithm scans the matrix to detect sequences and then manipulates columns to simulate gravity. No additional complex structures are required beyond the board itself.

What is the time complexity of Candy Crush?

The typical simulation solution runs in O(m*n*max(m,n)) time. Each iteration scans the entire board to detect matches and then performs a gravity pass per column. Since the board can change multiple times before stabilizing, several iterations may occur before no more candies can be crushed.

Description Hints 1 Solution Video 25:39

723. Candy Crush

Medium77.6% acceptance11 companiesPremium elsewhere, free here

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

Given an m x n integer array board representing the grid of candy where board[i][j] represents the type of candy. A value of board[i][j] == 0 represents that the cell 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 (i.e., the board is stable), then return the current board.

You need to perform the above rules until the board becomes stable, then return the stable board.

Example 1:

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]]

Example 2:

Input: board = [[1,3,5,5,2],[3,4,3,3,1],[3,2,4,5,2],[2,4,4,5,5],[1,4,4,1,1]]
Output: [[1,3,0,0,0],[3,4,0,5,2],[3,2,0,3,1],[2,4,0,5,2],[1,4,3,1,1]]

Constraints:

m == board.length
n == board[i].length
3 <= m, n <= 50
1 <= board[i][j] <= 2000

Asked at 11 companies

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Hints open one at a time

Hint 1

Carefully perform the "crush" and "gravity" steps. In the crush step, flag each candy that should be removed, then go through and crush each flagged candy. In the gravity step, collect the candy in each column and then rewrite the column appropriately. Do these steps repeatedly until there's no work left to do.

25:39

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1class Solution:
  def solve(self):
      pass


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Examples

Case 1Case 2

Input

[[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]]

Input

[[1,3,5,5,2],[3,4,3,3,1],[3,2,4,5,2],[2,4,4,5,5],[1,4,4,1,1]]

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