Hash from two arrays: Difference between revisions
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from itertools import izip |
from itertools import izip |
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hash = dict(izip(keys, values)) |
hash = dict(izip(keys, values)) |
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</lang> |
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{{works with|Python|3.0+}} |
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Shows off the dict comprehensions in Python 3: |
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<lang python> |
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keys = ['a', 'b', 'c'] |
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values = [1, 2, 3] |
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hash = {key: value for key, value in zip(keys, values)} |
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</lang> |
</lang> |
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Revision as of 10:47, 27 February 2009
![Task](http://static.miraheze.org/rosettacodewiki/thumb/b/ba/Rcode-button-task-crushed.png/64px-Rcode-button-task-crushed.png)
You are encouraged to solve this task according to the task description, using any language you may know.
Using two Arrays of equal length, create a Hash object where the elements from one array (the keys) are linked to the elements of the other (the values)
ActionScript
<lang actionscript> package {
public class MyClass { public static function main():Void { var hash:Object = new Object(); var keys:Array = new Array("a", "b", "c"); var values:Array = new Array(1, 2, 3); for (var i:int = 0; i < keys.length(); i++) hash[keys[i]] = values[i]; } }
} </lang>
Ada
<lang ada>
with Ada.Strings.Hash; with Ada.Containers.Hashed_Maps; with Ada.Text_Io; with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; procedure Hash_Map_Test is function Equivalent_Key (Left, Right : Unbounded_String) return Boolean is begin return Left = Right; end Equivalent_Key; function Hash_Func(Key : Unbounded_String) return Ada.Containers.Hash_Type is begin return Ada.Strings.Hash(To_String(Key)); end Hash_Func; package My_Hash is new Ada.Containers.Hashed_Maps(Key_Type => Unbounded_String, Element_Type => Unbounded_String, Hash => Hash_Func, Equivalent_Keys => Equivalent_Key); type String_Array is array(Positive range <>) of Unbounded_String; Hash : My_Hash.Map; Key_List : String_Array := (To_Unbounded_String("foo"), To_Unbounded_String("bar"), To_Unbounded_String("val")); Element_List : String_Array := (To_Unbounded_String("little"), To_Unbounded_String("miss"), To_Unbounded_String("muffet")); begin for I in Key_List'range loop Hash.Insert(Key => (Key_List(I)), New_Item => (Element_List(I))); end loop; for I in Key_List'range loop Ada.Text_Io.Put_Line(To_String(Key_List(I)) & " => " & To_String(Hash.Element(Key_List(I)))); end loop; end Hash_Map_Test;
</lang>
C++
By strict definition a std::map is not a hash, but it provides the same functionality. The C++-200x update to the C++ standard is incorporating hashes. When they are standardized the code below can change std::map to std::unordered_map and this will technically be a hash table. The core idea, turning two sequences into an associative mapping, is valid either way.
#include <map> #include <string> int main( int argc, char* argv[] ) { std::string keys[] = { "1", "2", "3" } ; std::string vals[] = { "a", "b", "c" } ; std::map< std::string, std::string > hash ; for( int i = 0 ; i < 3 ; i++ ) { hash[ keys[i] ] = vals[i] ; } }
Alternatively:
#include <map> // for std::map #include <algorithm> // for std::transform #include <string> // for std::string #include <utility> // for std::make_pair int main() { std::string keys[] = { "one", "two", "three" }; std::string vals[] = { "foo", "bar", "baz" }; std::map<std::string, std::string> hash; std::transform(keys, keys+3, vals, std::inserter(hash, hash.end()), std::make_pair<std::string, std::string>); }
C#
System.Collections.HashTable h = new System.Collections.HashTable(); string[] arg_keys = {"foo","bar","val"}; string[] arg_values = {"little", "miss", "muffet"}; //Some basic error checking int arg_length = 0; if ( arg_keys.Length == arg_values.Length ) { arg_length = arg_keys.Length; } for( int i = 0; i < arg_length; i++ ){ h.add( arg_keys[i], arg_values[i] ); }
Alternate way of adding values
for( int i = 0; i < arg_length; i++ ){ h[ arg_keys[i] ] = arg_values[i]; }
D
string[] keys = ["one", "two", "three"] int[] values = [1, 2, 3]; int[string] hash; foreach(idx, key; keys) hash[key] = values[idx];
E
def keys := ["one", "two", "three"] def values := [1, 2, 3] __makeMap.fromColumns(keys, values)
Factor
USING: hashtables ; { "one" "two" "three" } { 1 2 3 } zip >hashtable
Groovy
keys = ['a','b','c'] vals = ['aaa', 'bbb', 'ccc'] hash = [:] i = 0 keys.each { entry -> hash.put(entry, vals[i++]) }
Haskell
import Data.Map makeMap ks vs = fromList $ zip ks vs mymap = makeMap ['a','b','c'] [1,2,3]
J
f=: y {~ x&i.
For example:
x=: 10?.100 y=: > ;:'zero one two three four five six seven eight nine' f=: y {~ x&i. x 46 99 23 62 42 44 12 5 68 63 $y 10 5 f 46 zero f 99 one f 63 5 12 5 23 nine seven six seven two
Here, x is a list of 10 integers between 0 and 99 chosen at random without repetition, and y is a 10 by 5 character matrix.
Java
import java.util.HashMap; public static void main(String[] args){ String[] keys= {"a", "b", "c"}; int[] vals= {1, 2, 3}; HashMap<String, Integer> hash= new HashMap<String, Integer>(); for(int i= 0; i < keys.length; i++){ hash.put(keys[i], vals[i]); } }
JavaScript
var keys = ['a', 'b', 'c']; var values = [1, 2, 3]; var map = {}; for(var i in keys) { map[ keys[i] ] = values[i]; }
Objective-C
NSArray *keys = [NSArray arrayWithObjects:@"a", @"b", @"c", nil]; NSArray *values = [NSArray arrayWithObjects:[NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], nil]; NSDictionary *dict = [NSDictionary dictionaryWithObjects:values forKeys:keys];
OCaml
The idiomatic solution uses lists rather than arrays.
let keys = [ "foo"; "bar"; "baz" ] and vals = [ 16384; 32768; 65536 ] and hash = Hashtbl.create 0;;
List.iter2 (Hashtbl.add hash) keys vals;;
In the extremely unlikely event that it was actually necessary to use arrays, the solution would become slightly less elegant: (except using the ExtLib which provides the equivalent Array.iter2)
let keys = [| "foo"; "bar"; "baz" |] and vals = [| 16384; 32768; 65536 |] and hash = Hashtbl.create 0;;
for i = 0 to Array.length keys - 1 do Hashtbl.add hash keys.(i) vals.(i) done;;
In either case, an exception is raised if the inputs are different lengths.
Perl
use List::MoreUtils qw(zip); my @keys = qw(a b c); my @vals = (1, 2, 3); my %hash = zip @keys, @vals;
Using no modules:
my %hash; @hash{qw(a b c)} = (1, 2, 3);
PHP
$keys = array('a', 'b', 'c'); $values = array(1, 2, 3); $hash = array_combine($keys, $values);
$keys = array('a', 'b', 'c'); $values = array(1, 2, 3); $hash = array(); for ($idx = 0; $idx < count($keys); $idx++) { $hash[$keys[$idx]] = $values[$idx]; }
Pop11
vars keys = { 1 a b c}; vars vals = { 2 3 valb valc}; vars i; ;;; Create hash table vars ht = newmapping([], 500, 0, true); ;;; Loop over input arrays (vectors) for i from 1 to length(keys) do vals(i) -> ht(keys(i)); endfor;
Prolog
% this one with side effect hash table creation :-dynamic hash/2. make_hash([],[]). make_hash([H|Q],[H1|Q1]):- assert(hash(H,H1)), make_hash(Q,Q1). :-make_hash([un,deux,trois],[[a,b,c],[d,e,f],[g,h,i]]) % this one without side effects make_hash_pure([],[],[]). make_hash_pure([H|Q],[H1|Q1],[hash(H,H1)|R]):- make_hash_pure(Q,Q1,R). :-make_hash_pure([un,deux,trois],[[a,b,c],[d,e,f],[g,h,i]],L),findall(M,(member(M,L),assert(M)),L).
Python
<lang python> keys = ['a', 'b', 'c'] values = [1, 2, 3] hash = dict(zip(keys, values))
- Lazily:
from itertools import izip hash = dict(izip(keys, values)) </lang>
Shows off the dict comprehensions in Python 3: <lang python> keys = ['a', 'b', 'c'] values = [1, 2, 3] hash = {key: value for key, value in zip(keys, values)} </lang>
(any version)
<lang python>keys = ['a', 'b', 'c'] values = [1, 2, 3] hash = {} for i range(len(keys)):
hash[keys[i]] = values[i]
</lang> The original (Ruby) example uses a range of different types as keys. Here is similar in python (run at the shell): <lang python>>>> class Hashable(object): def __hash__(self): return id(self) ^ 0xBEEF
>>> my_inst = Hashable()
>>> my_int = 1
>>> my_complex = 0 + 1j
>>> my_float = 1.2
>>> my_string = "Spam"
>>> my_bool = True
>>> my_unicode = u'Ham'
>>> my_list = ['a', 7]
>>> my_tuple = ( 0.0, 1.4 )
>>> my_set = set(my_list)
>>> def my_func():
pass
>>> class my_class(object): pass
>>> keys = [my_inst, my_tuple, my_int, my_complex, my_float, my_string, my_bool, my_unicode, frozenset(my_set), tuple(my_list), my_func, my_class] >>> values = range(12) >>> d = dict(zip(keys, values)) >>> for key, value in d.items(): print key, ":", value
1 : 6 1j : 3 Ham : 7 Spam : 5 (0.0, 1.3999999999999999) : 1 frozenset(['a', 7]) : 8 1.2 : 4 ('a', 7) : 9 <function my_func at 0x0128E7B0> : 10 <class '__main__.my_class'> : 11 <__main__.Hashable object at 0x012AFC50> : 0 >>> </lang>
Raven
[ 'a' 'b' 'c' ] as $keys [ 1 2 3 ] as $vals $keys $vals combine as $hash
Ruby
keys=['hal',666,[1,2,3]] vals=['ibm','devil',123] hash = Hash[*keys.zip(vals).flatten] # now hash => {'hal' => 'ibm', 666 => 'devil', [1,2,3] => 123}
#retrieve the value linked to the key [1,2,3] puts hash[ [1,2,3] ] #123
Scala
val keys = Array(1, 2, 3) val values = Array("A", "B", "C") val map = Map(keys.zip(values) : _*) // returns Map(1 -> "A", 2 -> "B", 3 -> "C") // keys.zip(values) is an array of pairs : Array((1, "A"), (2, "B"), (3, "C")) // Map(...) expects multiple pairs arguments. Syntax ": _*" tells the single argument contains multiple values.
Scheme
Using SRFI 69:
<lang scheme>(define (lists->hash-table keys values . rest) (apply alist->hash-table (map cons keys values) rest))</lang>
Seed7
$ include "seed7_05.s7i"; const type: numericHash is hash [string] integer; var numericHash: myHash is numericHash.value; const proc: main is func local var array string: keyList is [] ("one", "two", "three"); var array integer: valueList is [] (1, 2, 3); var integer: number is 0; begin for number range 1 to length(keyList) do myHash @:= [keyList[number]] valueList[number]; end for; end func;
Tcl
Arrays in Tcl are automatically associative, i.e. there are no "not hashed arrays". If we can take "arrays of equal length" to mean "lists of equal length", then the task might look like this:
set keys [list fred bob joe] set values [list barber plumber tailor] array set arr {} foreach a $keys b $values { set $arr($a) $b }
UnixPipes
Using a sorted file as an associative array (see Creating an associative array for usage.)
cat <<VAL >p.values apple boy cow dog elephant VAL
cat <<KEYS >p.keys a b c d e KEYS
paste -d\ <(cat p.values | sort) <(cat p.keys | sort)
Visual Basic .NET
Dim names = New String() {"Frank", "Tom", "Jones"} Dim grades = New Integer() {90, 87, 96}
Dim hash = New Dictionary(Of String, Integer) For i = 0 To names.Length - 1 hash.Add(names(i), grades(i)) Next