Class BinarySearchST<Key extends Comparable<Key>,Value>
- Object
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- edu.princeton.cs.algs4.BinarySearchST<Key,Value>
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public class BinarySearchST<Key extends Comparable<Key>,Value> extends Object
TheBST
class represents an ordered symbol table of generic key-value pairs. It supports the usual put, get, contains, delete, size, and is-empty methods. It also provides ordered methods for finding the minimum, maximum, floor, select, and ceiling. It also provides a keys method for iterating over all of the keys. A symbol table implements the associative array abstraction: when associating a value with a key that is already in the symbol table, the convention is to replace the old value with the new value. UnlikeMap
, this class uses the convention that values cannot benull
—setting the value associated with a key tonull
is equivalent to deleting the key from the symbol table.It requires that the key type implements the
Comparable
interface and calls thecompareTo()
and method to compare two keys. It does not call eitherequals()
orhashCode()
.This implementation uses a sorted array. The put and remove operations take Θ(n) time in the worst case. The contains, ceiling, floor, and rank operations take Θ(log n) time in the worst case. The size, is-empty, minimum, maximum, and select operations take Θ(1) time. Construction takes Θ(1) time.
For alternative implementations of the symbol table API, see
ST
,BST
,SequentialSearchST
,RedBlackBST
,SeparateChainingHashST
, andLinearProbingHashST
, For additional documentation, see Section 3.1 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
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Constructor Summary
Constructors Constructor Description BinarySearchST()
Initializes an empty symbol table.BinarySearchST(int capacity)
Initializes an empty symbol table with the specified initial capacity.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Key
ceiling(Key key)
Returns the smallest key in this symbol table greater than or equal tokey
.boolean
contains(Key key)
Does this symbol table contain the given key?void
delete(Key key)
Removes the specified key and associated value from this symbol table (if the key is in the symbol table).void
deleteMax()
Removes the largest key and associated value from this symbol table.void
deleteMin()
Removes the smallest key and associated value from this symbol table.Key
floor(Key key)
Returns the largest key in this symbol table less than or equal tokey
.Value
get(Key key)
Returns the value associated with the given key in this symbol table.boolean
isEmpty()
Returns true if this symbol table is empty.Iterable<Key>
keys()
Returns all keys in this symbol table as anIterable
.Iterable<Key>
keys(Key lo, Key hi)
Returns all keys in this symbol table in the given range, as anIterable
.static void
main(String[] args)
Unit tests theBinarySearchST
data type.Key
max()
Returns the largest key in this symbol table.Key
min()
Returns the smallest key in this symbol table.void
put(Key key, Value val)
Inserts the specified key-value pair into the symbol table, overwriting the old value with the new value if the symbol table already contains the specified key.int
rank(Key key)
Returns the number of keys in this symbol table strictly less thankey
.Key
select(int k)
Return the kth smallest key in this symbol table.int
size()
Returns the number of key-value pairs in this symbol table.int
size(Key lo, Key hi)
Returns the number of keys in this symbol table in the specified range.
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Method Detail
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size
public int size()
Returns the number of key-value pairs in this symbol table.- Returns:
- the number of key-value pairs in this symbol table
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isEmpty
public boolean isEmpty()
Returns true if this symbol table is empty.- Returns:
true
if this symbol table is empty;false
otherwise
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contains
public boolean contains(Key key)
Does this symbol table contain the given key?- Parameters:
key
- the key- Returns:
true
if this symbol table containskey
andfalse
otherwise- Throws:
IllegalArgumentException
- ifkey
isnull
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get
public Value get(Key key)
Returns the value associated with the given key in this symbol table.- Parameters:
key
- the key- Returns:
- the value associated with the given key if the key is in the symbol table
and
null
if the key is not in the symbol table - Throws:
IllegalArgumentException
- ifkey
isnull
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rank
public int rank(Key key)
Returns the number of keys in this symbol table strictly less thankey
.- Parameters:
key
- the key- Returns:
- the number of keys in the symbol table strictly less than
key
- Throws:
IllegalArgumentException
- ifkey
isnull
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put
public void put(Key key, Value val)
Inserts the specified key-value pair into the symbol table, overwriting the old value with the new value if the symbol table already contains the specified key. Deletes the specified key (and its associated value) from this symbol table if the specified value isnull
.- Parameters:
key
- the keyval
- the value- Throws:
IllegalArgumentException
- ifkey
isnull
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delete
public void delete(Key key)
Removes the specified key and associated value from this symbol table (if the key is in the symbol table).- Parameters:
key
- the key- Throws:
IllegalArgumentException
- ifkey
isnull
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deleteMin
public void deleteMin()
Removes the smallest key and associated value from this symbol table.- Throws:
NoSuchElementException
- if the symbol table is empty
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deleteMax
public void deleteMax()
Removes the largest key and associated value from this symbol table.- Throws:
NoSuchElementException
- if the symbol table is empty
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min
public Key min()
Returns the smallest key in this symbol table.- Returns:
- the smallest key in this symbol table
- Throws:
NoSuchElementException
- if this symbol table is empty
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max
public Key max()
Returns the largest key in this symbol table.- Returns:
- the largest key in this symbol table
- Throws:
NoSuchElementException
- if this symbol table is empty
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select
public Key select(int k)
Return the kth smallest key in this symbol table.- Parameters:
k
- the order statistic- Returns:
- the
k
th smallest key in this symbol table - Throws:
IllegalArgumentException
- unlessk
is between 0 and n–1
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floor
public Key floor(Key key)
Returns the largest key in this symbol table less than or equal tokey
.- Parameters:
key
- the key- Returns:
- the largest key in this symbol table less than or equal to
key
- Throws:
NoSuchElementException
- if there is no such keyIllegalArgumentException
- ifkey
isnull
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ceiling
public Key ceiling(Key key)
Returns the smallest key in this symbol table greater than or equal tokey
.- Parameters:
key
- the key- Returns:
- the smallest key in this symbol table greater than or equal to
key
- Throws:
NoSuchElementException
- if there is no such keyIllegalArgumentException
- ifkey
isnull
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size
public int size(Key lo, Key hi)
Returns the number of keys in this symbol table in the specified range.- Parameters:
lo
- minimum endpointhi
- maximum endpoint- Returns:
- the number of keys in this symbol table between
lo
(inclusive) andhi
(inclusive) - Throws:
IllegalArgumentException
- if eitherlo
orhi
isnull
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keys
public Iterable<Key> keys()
Returns all keys in this symbol table as anIterable
. To iterate over all of the keys in the symbol table namedst
, use the foreach notation:for (Key key : st.keys())
.- Returns:
- all keys in this symbol table
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keys
public Iterable<Key> keys(Key lo, Key hi)
Returns all keys in this symbol table in the given range, as anIterable
.- Parameters:
lo
- minimum endpointhi
- maximum endpoint- Returns:
- all keys in this symbol table between
lo
(inclusive) andhi
(inclusive) - Throws:
IllegalArgumentException
- if eitherlo
orhi
isnull
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main
public static void main(String[] args)
Unit tests theBinarySearchST
data type.- Parameters:
args
- the command-line arguments
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