# 212. Word Search II

## Hard

***

Given an `m x n` `board` of characters and a list of strings `words`, return *all words on the board*.

Each word must be constructed from letters of sequentially adjacent cells, where **adjacent cells** are horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.

 

**Example 1:**

![](https://assets.leetcode.com/uploads/2020/11/07/search1.jpg)

```
Input: board = [["o","a","a","n"],["e","t","a","e"],["i","h","k","r"],["i","f","l","v"]], words = ["oath","pea","eat","rain"]
Output: ["eat","oath"]
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2020/11/07/search2.jpg)

```
Input: board = [["a","b"],["c","d"]], words = ["abcb"]
Output: []
```

 

**Constraints:**

* `m == board.length`
* `n == board[i].length`
* `1 <= m, n <= 12`
* `board[i][j]` is a lowercase English letter.
* `1 <= words.length <= 3 * 104`
* `1 <= words[i].length <= 10`
* `words[i]` consists of lowercase English letters.
* All the strings of `words` are unique.