• Home
• com.github.javadev
• leetcode-in-java
• 1.17
• source code
• readme.md

×

Project download

Many resources are needed to download a project. Please understand that we have to compensate our server costs. Thank you in advance.
Project price only 1 $

You can buy this project and download/modify it how often you want.

g0101_0200.s0130_surrounded_regions.readme.md Maven / Gradle / Ivy

130\. Surrounded Regions

Medium

Given an `m x n` matrix `board` containing `'X'` and `'O'`, _capture all regions that are 4-directionally surrounded by_ `'X'`.

A region is **captured** by flipping all `'O'`s into `'X'`s in that surrounded region.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/02/19/xogrid.jpg)

**Input:** board = [["X","X","X","X"],["X","O","O","X"],["X","X","O","X"],["X","O","X","X"]]

**Output:** [["X","X","X","X"],["X","X","X","X"],["X","X","X","X"],["X","O","X","X"]]

**Explanation:** Surrounded regions should not be on the border, which means that any 'O' on the border of the board are not flipped to 'X'. Any 'O' that is not on the border and it is not connected to an 'O' on the border will be flipped to 'X'. Two cells are connected if they are adjacent cells connected horizontally or vertically. 

**Example 2:**

**Input:** board = [["X"]]

**Output:** [["X"]] 

**Constraints:**

*   `m == board.length`
*   `n == board[i].length`
*   `1 <= m, n <= 200`
*   `board[i][j]` is `'X'` or `'O'`.