> For the complete documentation index, see [llms.txt](https://jaywin.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jaywin.gitbook.io/leetcode/solutions/0827-making-a-large-island.md).

# 0827. Making A Large Island

<https://leetcode.com/problems/making-a-large-island>

## Description

You are given an `n x n` binary matrix `grid`. You are allowed to change **at most one** `0` to be `1`.

Return *the size of the largest **island** in* `grid` *after applying this operation*.

An **island** is a 4-directionally connected group of `1`s.

**Example 1:**

```

**Input:** grid = [[1,0],[0,1]]
**Output:** 3
**Explanation:** Change one 0 to 1 and connect two 1s, then we get an island with area = 3.
```

**Example 2:**

```

**Input:** grid = [[1,1],[1,0]]
**Output:** 4
**Explanation:** Change the 0 to 1 and make the island bigger, only one island with area = 4.
```

**Example 3:**

```

**Input:** grid = [[1,1],[1,1]]
**Output:** 4
**Explanation:** Can't change any 0 to 1, only one island with area = 4.
```

**Constraints:**

* `n == grid.length`
* `n == grid[i].length`
* `1 <= n <= 500`
* `grid[i][j]` is either `0` or `1`.

## ac

```java
```