LeetCode 1596: The Most Frequently Ordered Products for Each Customer Solution

import java.util.*;

class Solution {
    public List<List<String>> mostFrequentProducts(List<List<String>> orders) {
        Map<String, Map<String, Integer>> freqMap = new HashMap<>();
        
        for (List<String> order : orders) {
            String customer = order.get(0);
            String product = order.get(1);
            
            if (!freqMap.containsKey(customer)) {
                freqMap.put(customer, new HashMap<>());
            }
            freqMap.get(customer).put(product, freqMap.get(customer).getOrDefault(product, 0) + 1);
        }
        
        List<List<String>> result = new ArrayList<>();
        
        for (String customer : freqMap.keySet()) {
            List<String> mostFrequent = new ArrayList<>();
            int maxFreq = 0;
            
            for (String product : freqMap.get(customer).keySet()) {
                int freq = freqMap.get(customer).get(product);
                if (freq > maxFreq) {
                    mostFrequent.clear();
                    mostFrequent.add(product);
                    maxFreq = freq;
                } else if (freq == maxFreq) {
                    mostFrequent.add(product);
                }
            }
            
            result.add(mostFrequent);
        }
        
        return result;
    }
}