我们可以将散列 table 放在散列 table 中吗？

Question

我们可以 link 为每个键在哈希 table 中使用另一个哈希 table 吗？

我的目标是拥有一个非常快速的二维数据结构来存储电子表格中的单元格。

我将 "all columns within a row" 存储在散列 table 中。然后对所有 'r' 行执行此操作。接下来为行创建最终散列 table，并将所有 'r' 个散列 table 存储在新散列 table 中。这种方式有效吗？或者有更好的方法吗？

Answer 1

怎么样

Map<String, Map<Integer,Integer>> asdf = new HashMap<String, Map<Integer, Integer>>();

但老实说，您应该先将其包装在一个对象中。在这种结构下全局会很不方便。

你可以试试这个 BiHashMap

public class BiHashMap<K1, K2, V> {

private final Map<K1, Map<K2, V>> mMap;

public BiHashMap() {
    mMap = new HashMap<K1, Map<K2, V>>();
}

/**
 * Associates the specified value with the specified keys in this map (optional operation). If the map previously
 * contained a mapping for the key, the old value is replaced by the specified value.
 * 
 * @param key1
 *            the first key
 * @param key2
 *            the second key
 * @param value
 *            the value to be set
 * @return the value previously associated with (key1,key2), or <code>null</code> if none
 * @see Map#put(Object, Object)
 */
public V put(K1 key1, K2 key2, V value) {
    Map<K2, V> map;
    if (mMap.containsKey(key1)) {
        map = mMap.get(key1);
    } else {
        map = new HashMap<K2, V>();
        mMap.put(key1, map);
    }

    return map.put(key2, value);
}

/**
 * Returns the value to which the specified key is mapped, or <code>null</code> if this map contains no mapping for
 * the key.
 * 
 * @param key1
 *            the first key whose associated value is to be returned
 * @param key2
 *            the second key whose associated value is to be returned
 * @return the value to which the specified key is mapped, or <code>null</code> if this map contains no mapping for
 *         the key
 * @see Map#get(Object)
 */
public V get(K1 key1, K2 key2) {
    if (mMap.containsKey(key1)) {
        return mMap.get(key1).get(key2);
    } else {
        return null;
    }
}

/**
 * Returns <code>true</code> if this map contains a mapping for the specified key
 * 
 * @param key1
 *            the first key whose presence in this map is to be tested
 * @param key2
 *            the second key whose presence in this map is to be tested
 * @return Returns true if this map contains a mapping for the specified key
 * @see Map#containsKey(Object)
 */
public boolean containsKeys(K1 key1, K2 key2) {
    return mMap.containsKey(key1) && mMap.get(key1).containsKey(key2);
}

public void clear() {
    mMap.clear();
}

}

然后像这样创建使用它：

BiHashMap<String,String,String> bigBoard = new BiHashMap<String,String,String>();

我们可以将散列 table 放在散列 table 中吗？

Can we put hash tables inside a hash table?

java

hashtable

spreadsheet