Package 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

Modifier and Type
Method
Description
`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 Details

### 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.