org.apache.lucene.search.suggest.tst

## Class TSTAutocomplete

- java.lang.Object
- - org.apache.lucene.search.suggest.tst.TSTAutocomplete

    public class TSTAutocomplete
    extends Object

Ternary Search Trie implementation.

See Also:
  `TernaryTreeNode`

### Method Summary

Methods
`void` `balancedTree(Object[] tokens, Object[] vals, int lo, int hi, TernaryTreeNode root)` Inserting keys in TST in the order middle,small,big (lexicographic measure) recursively creates a balanced tree which reduces insertion and search times significantly.
`TernaryTreeNode` `insert(TernaryTreeNode currentNode, CharSequence s, Object val, int x)` Inserts a key in TST creating a series of Binary Search Trees at each node.
`ArrayList<TernaryTreeNode>` `prefixCompletion(TernaryTreeNode root, CharSequence s, int x)` Auto-completes a given prefix query using Depth-First Search with the end of prefix as source node each time finding a new leaf to get a complete key to be added in the suggest list.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Method Detail

#### balancedTree

    public void balancedTree(Object[] tokens,
                    Object[] vals,
                    int lo,
                    int hi,
                    TernaryTreeNode root)

Inserting keys in TST in the order middle,small,big (lexicographic measure) recursively creates a balanced tree which reduces insertion and search times significantly.

Parameters:
  `tokens` - Sorted list of keys to be inserted in TST.
  `lo` - stores the lower index of current list.
  `hi` - stores the higher index of current list.
  `root` - a reference object to root of TST.

#### insert

    public TernaryTreeNode insert(TernaryTreeNode currentNode,
                         CharSequence s,
                         Object val,
                         int x)

Inserts a key in TST creating a series of Binary Search Trees at each node. The key is actually stored across the eqKid of each node in a successive manner.

Parameters:
  `currentNode` - a reference node where the insertion will take currently.
  `s` - key to be inserted in TST.
  `x` - index of character in key to be inserted currently.
Returns:
  currentNode The new reference to root node of TST

#### prefixCompletion

    public ArrayList<TernaryTreeNode> prefixCompletion(TernaryTreeNode root,
                                              CharSequence s,
                                              int x)

Auto-completes a given prefix query using Depth-First Search with the end of prefix as source node each time finding a new leaf to get a complete key to be added in the suggest list.

Parameters:
  `root` - a reference to root node of TST.
  `s` - prefix query to be auto-completed.
  `x` - index of current character to be searched while traversing through the prefix in TST.
Returns:
  suggest list of auto-completed keys for the given prefix query.