FinDev task

gistfile1.txt

public class ParseString2 {

    //stores mapping key -> string array of value and index in original string
    Map<String, List<String>> cache = new HashMap<>();

    //stores mapping index of key-value pair in original string -> key and position of value in list inside of cache
    Map<String, String[]> reverseCache = new TreeMap<>();

    public void parse(String str) {
        String[] keyValuePairs = str.split(";");
        for (int i = 0; i < keyValuePairs.length; i++) {
            String[] keyValue = keyValuePairs[i].split("=");
            String key = keyValue[0];
            String value = keyValue[1];
            List<String> cacheValues = cache.computeIfAbsent(key, k -> new ArrayList<>());
            cacheValues.add(value);
            String indexString = String.valueOf(i);
            reverseCache.computeIfAbsent(indexString, k -> new String[]{key, String.valueOf(cacheValues.size() - 1)});
        }
    }

    // No cache for original str
    public String getOriginal() {
        List<String> keyValuePairs = new ArrayList<>();
        reverseCache.values().forEach(keyAndIndex -> {
                    String key = keyAndIndex[0];
                    int index = Integer.parseInt(keyAndIndex[1]);
                    String value = cache.get(key).get(index);
                    keyValuePairs.add(key + "=" + value);
                }
        );

        return keyValuePairs.stream().collect(Collectors.joining(";"));
    }


    // O(1)
    public String getValues(String key) {
        if (cache.containsKey(key)) {
            List<String> values = cache.get(key);
            return values.get(values.size() - 1);
        }
        return null;
    }

    public static void main(String[] args) {
        String val = "key1=val1;key2=val2;key3=val3;key1=val4;key2=val6;key1=val6";
        ParseString2 ps = new ParseString2();
        ps.parse(val);

        System.out.println(ps.getOriginal());
        System.out.println(ps.getValues("key1"));
        System.out.println(ps.getValues("key2"));
        System.out.println(ps.getValues("key3"));
        System.out.println(ps.getValues("342342"));
    }
}