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.

**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]]Explanation:

**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].

```
struct Solution;
impl Solution {
fn candy_crush(mut board: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
let n = board.len();
let m = board[0].len();
let mut found = true;
let mut marked = vec![vec![false; m]; n];
while found {
found = false;
for i in 0..n {
for j in 0..m {
let val = board[i][j];
if val == 0 {
continue;
}
if j + 2 < m && board[i][j + 1] == val && board[i][j + 2] == val {
found = true;
let mut k = j;
while k < m && board[i][k] == val {
marked[i][k] = true;
k += 1;
}
}
if i + 2 < n && board[i + 1][j] == val && board[i + 2][j] == val {
found = true;
let mut k = i;
while k < n && board[k][j] == val {
marked[k][j] = true;
k += 1;
}
}
}
}
for i in 0..n {
for j in 0..m {
if marked[i][j] {
marked[i][j] = false;
board[i][j] = 0;
}
}
}
for j in 0..m {
let mut k = n;
for i in (0..n).rev() {
if board[i][j] > 0 {
let val = board[i][j];
board[i][j] = 0;
board[k - 1][j] = val;
k -= 1;
}
}
}
}
board
}
}
#[test]
fn test() {
let board: Vec<Vec<i32>> = [
[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],
]
.iter()
.map(|v| v.to_vec())
.collect();
let res: Vec<Vec<i32>> = [
[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],
]
.iter()
.map(|v| v.to_vec())
.collect();
assert_eq!(Solution::candy_crush(board), res);
}
```