247. Strobogrammatic Number II

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Find all strobogrammatic numbers that are of length = n.

Example:

```Input:  n = 2
Output: `["11","69","88","96"]`
```

247. Strobogrammatic Number II
``````struct Solution;
use std::collections::HashMap;

impl Solution {
fn find_strobogrammatic(n: i32) -> Vec<String> {
let mut res = vec![];
let hm: HashMap<char, char> =
vec![('0', '0'), ('1', '1'), ('6', '9'), ('8', '8'), ('9', '6')]
.into_iter()
.collect();
let n = n as usize;
let mut cur: Vec<char> = vec![];
Self::dfs(0, &mut cur, &mut res, &hm, n);
res
}

fn dfs(
i: usize,
cur: &mut Vec<char>,
all: &mut Vec<String>,
hm: &HashMap<char, char>,
n: usize,
) {
if i == n {
all.push(cur.iter().collect());
} else {
for (&k, &v) in hm {
if n != 1 && i == 0 && k == '0' {
continue;
}
let j = n - 1 - i;
if j < i && cur[j] != v {
continue;
}
if j == i && k != v {
continue;
}
cur.push(k);
Self::dfs(i + 1, cur, all, hm, n);
cur.pop();
}
}
}
}

#[test]
fn test() {
let n = 1;
let mut res = vec_string!["0", "1", "8"];
let mut ans = Solution::find_strobogrammatic(n);
res.sort();
ans.sort();
assert_eq!(ans, res);
let n = 2;
let mut res = vec_string!["11", "69", "88", "96"];
let mut ans = Solution::find_strobogrammatic(n);
res.sort();
ans.sort();
assert_eq!(ans, res);
}
``````