A sentence is a string of single-space separated words where each word consists only of lowercase letters.

A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence.

Given two sentences s1 and s2, return a list of all the uncommon words. You may return the answer in any order.

LeetCode Problem - 884

import java.util.*;

class Solution {
    public String[] uncommonFromSentences(String s1, String s2) {
        // Split the input sentences into arrays of words
        String[] s1Arr = s1.split(" ");
        String[] s2Arr = s2.split(" ");
        // Calculate the total length of the combined arrays
        int len = s1Arr.length + s2Arr.length;

        // Merge the arrays into a single array
        String[] s3Arr = new String[len];
        System.arraycopy(s1Arr, 0, s3Arr, 0, s1Arr.length);
        System.arraycopy(s2Arr, 0, s3Arr, s1Arr.length, s2Arr.length);

        // Count the occurrences of each word using a HashMap
        Map<String, Integer> mp = new HashMap<>();
        for (String s : s3Arr){
            mp.put(s, mp.getOrDefault(s, 0) + 1);
        }

        // Find words that occur only once
        List<String> al = new ArrayList<>();
        for (String s : s3Arr){
            if (mp.get(s) == 1){
                al.add(s);
            }
        }

        // Convert the list of uncommon words to an array
        String[] resultArr = new String[al.size()];
        for (int i=0; i<al.size(); i++){
            resultArr[i] = al.get(i);
        }

        // Return the array of uncommon words
        return resultArr;
    }
}