从平面地图表示中恢复价值树

Question

我有一个 Map<String, String> 类型的平面图，我想从中恢复原始值树 Map<String, Object>。树的元素可以是 Map<String, Object>，或 List<Object>，或只是 String。树的深度没有限制。例如：

public static void main(String[] args) {
    TreeMap<String, String> flatMap = new TreeMap<String, String>() {{
        put("1999.3:1", "23");
        put("1999.3:2", "24");
        put("1999.3:3", "25");
        put("1999.4:1", "1");
        put("1999.4:2", "2");
        put("1999.4:3.10", "42");
        put("2001.11.7:1", "23");
        put("2001.11.7:2", "24");
        put("2001.11.7:3", "25");
        put("2001.11.9:1", "1");
        put("2001.11.9:2", "2");
        put("2001.11.9:3", "3");
        put("2001.12", "45");
    }};
    System.out.println(flatMap);
}

平面图：

{1999.3:1=23, 1999.3:2=24, 1999.3:3=25, 1999.4:1=1, 1999.4:2=2, 1999.4:3.10=42,
 2001.11.7:1=23, 2001.11.7:2=24, 2001.11.7:3=25,
 2001.11.9:1=1, 2001.11.9:2=2, 2001.11.9:3=3, 2001.12=45}

原始值树：

{1999={3=[23, 24, 25], 4=[1, 2, {10=42}]},
 2001={11={7=[23, 24, 25], 9=[1, 2, 3]}, 12=45}}

^对面：.

Answer 1

迭代平面地图键并恢复原始树。对于从左到右的每个键，查找分隔符：

点 . - 嵌套对象是地图。下一个数字是地图中的关键。
冒号: - 嵌套对象是一个列表。下一个数字是列表中的索引（从 1 开始）。

然后递归处理嵌套对象，通过平面图的key向右移动：

public static void main(String[] args) {
    TreeMap<String, String> flatMap = new TreeMap<String, String>() {{
        put("1999.3:1", "23");
        put("1999.3:2", "24");
        put("1999.3:3", "25");
        put("1999.4:1", "1");
        put("1999.4:2", "2");
        put("1999.4:3.10", "42");
        put("2001.11.7:1", "23");
        put("2001.11.7:2", "24");
        put("2001.11.7:3", "25");
        put("2001.11.9:1", "1");
        put("2001.11.9:2", "2");
        put("2001.11.9:3", "3");
        put("2001.12", "45");
    }};
    TreeMap<String, Object> originalMap = new TreeMap<>();
    flatMap.forEach((key, value) -> processMap(key, value, originalMap));

    System.out.println(flatMap);
    System.out.println(originalMap);
}

@SuppressWarnings("unchecked")
private static void processMap(String flatMapKey,
                               String flatMapValue,
                               Map<String, Object> map) {
    int dot = flatMapKey.indexOf('.');
    int colon = flatMapKey.indexOf(':');

    // nested map
    if (dot > -1 && (dot < colon || colon == -1)) {
        String key = flatMapKey.substring(0, dot);
        Object nestedMap = map.get(key);
        if (nestedMap == null) {
            map.put(key, new TreeMap<>());
        }
        nestedMap = map.get(key);
        processMap(flatMapKey.substring(dot + 1),
                flatMapValue, (Map<String, Object>) nestedMap);
    }
    // nested list
    else if (colon > -1 && (colon < dot || dot == -1)) {
        String key = flatMapKey.substring(0, colon);
        Object nestedList = map.get(key);
        if (nestedList == null) {
            map.put(key, new ArrayList<>());
        }
        nestedList = map.get(key);
        processList(flatMapKey.substring(colon + 1),
                flatMapValue, (List<Object>) nestedList);
    }
    // insert value
    else if (dot == colon) {
        map.put(flatMapKey, flatMapValue);
    }
}

@SuppressWarnings("unchecked")
private static void processList(String flatMapKey,
                                String flatMapValue,
                                List<Object> list) {
    int dot = flatMapKey.indexOf('.');
    int colon = flatMapKey.indexOf(':');

    // nested map
    if (dot > -1 && (dot < colon || colon == -1)) {
        int index = Integer.parseInt(flatMapKey.substring(0, dot));
        while (list.size() < index) {
            list.add(null);
        }
        Object nestedMap = list.get(index - 1);
        if (nestedMap == null) {
            list.set(index - 1, new TreeMap<>());
        }
        nestedMap = list.get(index - 1);
        processMap(flatMapKey.substring(dot + 1),
                flatMapValue, (Map<String, Object>) nestedMap);
    }
    // nested list
    else if (colon > -1 && (colon < dot || dot == -1)) {
        int index = Integer.parseInt(flatMapKey.substring(0, colon));
        while (list.size() < index) {
            list.add(null);
        }
        Object nestedList = list.get(index - 1);
        if (nestedList == null) {
            list.set(index - 1, new ArrayList<>());
        }
        nestedList = list.get(index - 1);
        processList(flatMapKey.substring(colon + 1),
                flatMapValue, (List<Object>) nestedList);
    }
    // insert value
    else if (dot == colon) {
        int index = Integer.parseInt(flatMapKey);
        while (list.size() < index) {
            list.add(null);
        }
        list.set(index - 1, flatMapValue);
    }
}

平面图：

{1999.3:1=23, 1999.3:2=24, 1999.3:3=25, 1999.4:1=1, 1999.4:2=2, 1999.4:3.10=42,
 2001.11.7:1=23, 2001.11.7:2=24, 2001.11.7:3=25,
 2001.11.9:1=1, 2001.11.9:2=2, 2001.11.9:3=3, 2001.12=45}

原始树：

{1999={3=[23, 24, 25], 4=[1, 2, {10=42}]},
 2001={11={7=[23, 24, 25], 9=[1, 2, 3]}, 12=45}}

从平面地图表示中恢复价值树

Restoring a value tree from its flat map representation

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