212. Word Search II

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:

```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:

```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.

212. Word Search II
``````struct Solution;
use std::collections::HashMap;

#[derive(Default)]
struct Trie {
children: HashMap<char, Trie>,
end: Option<String>,
}

impl Trie {
fn insert(&mut self, word: String) {
for c in word.chars() {
}
}
}

impl Solution {
fn find_words(mut board: Vec<Vec<char>>, words: Vec<String>) -> Vec<String> {
let mut trie = Trie::default();
for word in words {
trie.insert(word);
}
let n = board.len();
let m = board[0].len();
let mut res: Vec<String> = vec![];
for i in 0..n {
for j in 0..m {
Self::dfs(i, j, &mut board, &mut res, &mut trie, n, m);
}
}
res.into_iter().collect()
}

fn dfs(
i: usize,
j: usize,
board: &mut Vec<Vec<char>>,
all: &mut Vec<String>,
trie: &mut Trie,
n: usize,
m: usize,
) {
let c = board[i][j];
if let Some(trie) = trie.children.get_mut(&c) {
board[i][j] = ' ';
if trie.end.is_some() {
all.push(trie.end.take().unwrap());
}
if i + 1 < n {
Self::dfs(i + 1, j, board, all, trie, n, m);
}
if j + 1 < m {
Self::dfs(i, j + 1, board, all, trie, n, m);
}
if i > 0 {
Self::dfs(i - 1, j, board, all, trie, n, m);
}
if j > 0 {
Self::dfs(i, j - 1, board, all, trie, n, m);
}
board[i][j] = c;
}
}
}

#[test]
fn test() {
let board = vec_vec_char![
['o', 'a', 'a', 'n'],
['e', 't', 'a', 'e'],
['i', 'h', 'k', 'r'],
['i', 'f', 'l', 'v']
];
let words = vec_string!["oath", "pea", "eat", "rain"];
let mut res = vec_string!["eat", "oath"];
let mut ans = Solution::find_words(board, words);
ans.sort();
res.sort();
assert_eq!(ans, res);
}
``````