# 0529. Minesweeper

<https://leetcode.com/problems/minesweeper>

## Description

Let's play the minesweeper game ([Wikipedia](https://en.wikipedia.org/wiki/Minesweeper_\(video_game\)), [online game](http://minesweeperonline.com))!

You are given an `m x n` char matrix `board` representing the game board where:

* `'M'` represents an unrevealed mine,
* `'E'` represents an unrevealed empty square,
* `'B'` represents a revealed blank square that has no adjacent mines (i.e., above, below, left, right, and all 4 diagonals),
* digit (`'1'` to `'8'`) represents how many mines are adjacent to this revealed square, and
* `'X'` represents a revealed mine.

You are also given an integer array `click` where `click = [clickr, clickc]` represents the next click position among all the unrevealed squares (`'M'` or `'E'`).

Return *the board after revealing this position according to the following rules*:

1. If a mine `'M'` is revealed, then the game is over. You should change it to `'X'`.
2. If an empty square `'E'` with no adjacent mines is revealed, then change it to a revealed blank `'B'` and all of its adjacent unrevealed squares should be revealed recursively.
3. If an empty square `'E'` with at least one adjacent mine is revealed, then change it to a digit (`'1'` to `'8'`) representing the number of adjacent mines.
4. Return the board when no more squares will be revealed.

**Example 1:**

![](https://assets.leetcode.com/uploads/2018/10/12/minesweeper_example_1.png)

```
**Input:** board = [["E","E","E","E","E"],["E","E","M","E","E"],["E","E","E","E","E"],["E","E","E","E","E"]], click = [3,0]
**Output:** [["B","1","E","1","B"],["B","1","M","1","B"],["B","1","1","1","B"],["B","B","B","B","B"]]
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2018/10/12/minesweeper_example_2.png)

```
**Input:** board = [["B","1","E","1","B"],["B","1","M","1","B"],["B","1","1","1","B"],["B","B","B","B","B"]], click = [1,2]
**Output:** [["B","1","E","1","B"],["B","1","X","1","B"],["B","1","1","1","B"],["B","B","B","B","B"]]
```

**Constraints:**

* `m == board.length`
* `n == board[i].length`
* `1 <= m, n <= 50`
* `board[i][j]` is either `'M'`, `'E'`, `'B'`, or a digit from `'1'` to `'8'`.
* `click.length == 2`
* `0 <= clickr < m`
* `0 <= clickc < n`
* `board[clickr][clickc]` is either `'M'` or `'E'`.

## ac

```java
class Solution {
    int[][] dirs = {{0,1},{0, -1},{1, 1},{1, -1},{1, 0},{-1, 0},{-1, -1},{-1, 1}};

    public char[][] updateBoard(char[][] board, int[] click) {
        // hit mine
        if (board[click[0]][click[1]] == 'M') {
            board[click[0]][click[1]] = 'X';
            return board;
        }

        int row = board.length, col = board[0].length;
        boolean[][] visited = new boolean[row][col];

        Queue<int[]> q = new LinkedList<>();
        q.offer(click);
        while (!q.isEmpty()) {
            int[] curr = q.poll();
            int cnt = 0;
            List<int[]> next = new ArrayList<>();
            for (int[] d : dirs) {
                int r = curr[0] + d[0];
                int c = curr[1] + d[1];
                if (r < 0 || r >= row || c < 0 || c >= col) continue;
                if (board[r][c] == 'M') cnt++; // meet one mine 
                if (!visited[r][c] && board[r][c] == 'E') next.add(new int[]{r, c});
                visited[r][c] = true;
            }
            if (cnt == 0) { // empty safe cell
                board[curr[0]][curr[1]] = 'B';
                for (int[] t : next) q.offer(t);
            } else {
                board[curr[0]][curr[1]] = (char)('0'+cnt);
                for (int[] t : next) visited[t[0]][t[1]] = false; // release back
            }
        }

        return board;
    }
}

/*
BFS, 1) count neighbor mines, add unvisited cells to tmp list; 2) if cnt == 0, update blank cell, add tmp list to next visit; if cnt > 0, update mines number, set tmp list cells unvisited
*/
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://jaywin.gitbook.io/leetcode/solutions/0529-minesweeper.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.