2085. Count Common Words With One Occurrence

Given two string arrays `words1` and `words2`, return the number of strings that appear exactly once in each of the two arrays.

Example 1:

```Input: words1 = ["leetcode","is","amazing","as","is"], words2 = ["amazing","leetcode","is"]
Output: 2
Explanation:
- "leetcode" appears exactly once in each of the two arrays. We count this string.
- "amazing" appears exactly once in each of the two arrays. We count this string.
- "is" appears in each of the two arrays, but there are 2 occurrences of it in words1. We do not count this string.
- "as" appears once in words1, but does not appear in words2. We do not count this string.
Thus, there are 2 strings that appear exactly once in each of the two arrays.
```

Example 2:

```Input: words1 = ["b","bb","bbb"], words2 = ["a","aa","aaa"]
Output: 0
Explanation: There are no strings that appear in each of the two arrays.
```

Example 3:

```Input: words1 = ["a","ab"], words2 = ["a","a","a","ab"]
Output: 1
Explanation: The only string that appears exactly once in each of the two arrays is "ab".
```

Constraints:

• `1 <= words1.length, words2.length <= 1000`
• `1 <= words1[i].length, words2[j].length <= 30`
• `words1[i]` and `words2[j]` consists only of lowercase English letters.

2085. Count Common Words With One Occurrence
``````struct Solution;

use std::collections::HashMap;

impl Solution {
fn count_words(words1: Vec<String>, words2: Vec<String>) -> i32 {
let mut hm1: HashMap<String, usize> = HashMap::new();
let mut hm2: HashMap<String, usize> = HashMap::new();
for w in words1 {
*hm1.entry(w).or_default() += 1;
}
for w in words2 {
*hm2.entry(w).or_default() += 1;
}
let mut res = 0;
for (k, v) in hm1 {
if v == 1 && *hm2.get(&k).unwrap_or(&0) == 1 {
res += 1;
}
}
res
}
}

#[test]
fn test() {
let words1 = vec_string!["leetcode", "is", "amazing", "as", "is"];
let words2 = vec_string!["amazing", "leetcode", "is"];
let res = 2;
assert_eq!(Solution::count_words(words1, words2), res);
let words1 = vec_string!["b", "bb", "bbb"];
let words2 = vec_string!["a", "aa", "aaa"];
let res = 0;
assert_eq!(Solution::count_words(words1, words2), res);
let words1 = vec_string!["a", "ab"];
let words2 = vec_string!["a", "a", "a", "ab"];
let res = 1;
assert_eq!(Solution::count_words(words1, words2), res);
}
``````