Lintcode 502. Mini Cassandra

Description

中文English

Cassandra is a NoSQL database (a.k.a key-value storage). One individual data entry in cassandra constructed by 3 parts:

1. row_key. (a.k.a hash_key, partition key or sharding_key.)
2. column_key.
3. value

row_key is used to hash and can not support range query. Let's simplify this to a string.
column_key is sorted and support range query. Let's simplify this to integer.
value is a string. You can serialize any data into a string and store it in value.

Implement the following methods:

1. insert(row_key, column_key, value)
2. query(row_key, column_start, column_end) return a list of entries

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Example

Example 1:

Input:
  insert("google", 1, "haha")
  query("google", 0, 1)
Output: [(1, "haha")]

Example 2:

Input:
  insert("google", 1, "haha")
  insert("lintcode", 1, "Good")
  insert("google", 2, "hehe")
  query("google", 0, 1)
  query("google", 0, 2)
  query("go", 0, 1)
  query("lintcode", 0, 10)
Output:
  [(1, "haha")]
  [(1, "haha"),(2, "hehe")]
  []
  [(1, "Good")]

Code (Java):

/**
 * Definition of Column:
 * public class Column {
 *     public int key;
 *     public String value;
 *     public Column(int key, String value) {
 *         this.key = key;
 *         this.value = value;
 *    }
 * }
 */


public class MiniCassandra {
    Map<String, TreeMap<Integer, Column>> rowMap;
    public MiniCassandra() {
        // do intialization if necessary
        rowMap = new HashMap<>();
    }

    /*
     * @param raw_key: a string
     * @param column_key: An integer
     * @param column_value: a string
     * @return: nothing
    */

    public void insert(String row_key, int column_key, String value) {
        // write your code here
        TreeMap<Integer, Column> columnMap = rowMap.getOrDefault(row_key, new TreeMap<>());
        Column column = new Column(column_key, value);
        columnMap.put(column_key, column);
        rowMap.put(row_key, columnMap);
    }

    /*
     * @param row_key: a string
     * @param column_start: An integer
     * @param column_end: An integer
     * @return: a list of Columns
     */
    public List<Column> query(String row_key, int column_start, int column_end) {
        if (!rowMap.containsKey(row_key)) {
            return new ArrayList<Column>();
        }
        
        TreeMap<Integer, Column> columnMap = rowMap.get(row_key);
        NavigableMap<Integer, Column> rangeMap = columnMap.subMap(column_start, true, column_end, true);
        List<Column> ans = new ArrayList<>();
        for (Integer key : rangeMap.keySet()) {
            ans.add(rangeMap.get(key));
        }

        return ans;
    }
}