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

LeetCode Problem - 2085

class Solution {
    public int countWords(String[] words1, String[] words2) {
        // Variable to store the count of words appearing exactly once in both arrays
        int result = 0;
        // HashMap to store the frequency of words in words1
        HashMap<String, Integer> hm1 = new HashMap<>();
        // HashMap to store the frequency of words in words2
        HashMap<String, Integer> hm2 = new HashMap<>();

        // Count the frequency of words in words1
        for (String str : words1) {
            hm1.put(str, hm1.getOrDefault(str, 0) + 1);
        }
        // Count the frequency of words in words2
        for (String str : words2) {
            hm2.put(str, hm2.getOrDefault(str, 0) + 1);
        }

        // Iterate through each word in words1
        for (String word : words1) {
            // If the word appears exactly once in both words1 and words2, increment the result
            if (hm1.get(word) == 1 && hm2.getOrDefault(word, 0) == 1) {
                result++;
            }
        }

        // Return the count of words appearing exactly once in both arrays
        return result;
    }
}