Hash from two arrays: Difference between revisions
(-> Tcl) |
(→[[Ruby]]: make code more idiomatic) |
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keys=['hal',666,[1,2,3]] |
keys=['hal',666,[1,2,3]] |
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vals=['ibm','devil',123] |
vals=['ibm','devil',123] |
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hash= |
hash = Hash[*keys.zip(vals)] |
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⚫ | |||
keys.zip(vals).each {|key,val| hash[key] = val} |
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⚫ | |||
#retrieve the value linked to the key [1,2,3] |
#retrieve the value linked to the key [1,2,3] |
Revision as of 16:02, 16 February 2007
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 on array (the keys) are linked to the elements of the other (the values)
C++
By strict definition a std::map is not a hash, but it provides the same functionality (but note that some C++ has hash sets too).
Compiler: g++ 4.0.2
#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
char[][] keys = ["one", "two", "three"] int[] values = [1, 2, 3]; int[char[]] hash; foreach(i,k; keys) hash[k] = values[i];
Haskell
Interpreter: GHCi 6.6
import Data.Map makeMap ks vs = fromList $ zip ks vs mymap = makeMap ['a','b','c'] [1,2,3]
JavaScript
var keys = ['a', 'b', 'c']; var values = [1, 2, 3]; var map = {}; for(var i in keys) { map[ keys[i] ] = values[i]; }
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:
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
Interpreter: Perl 5.8.8
Short
my @keys = ('a', 'b', 'c'); my @vals = (1, 2, 3); my %hash; @hash{@keys} = @vals;
Mid Length
my @keys = ('a', 'b', 'c'); my @vals = (1, 2, 3); my %hash; $hash{$keys[$_]} = $vals[$_] for (0 .. $#keys);
Long
my @keys = ('a', 'b', 'c'); my @vals = (1, 2, 3); my %hash; foreach my $idx (0..$#keys){ $hash{$keys[$idx]} = $vals[$idx]; }
PHP
PHP 5:
$keys = array('a', 'b', 'c'); $values = array(1, 2, 3); $hash = array_combine($keys, $values);
PHP 4:
$keys = array('a', 'b', 'c'); $values = array(1, 2, 3); $hash = array(); for ($idx = 0; $idx < count($keys); $idx++) { $hash[$keys[$idx]] = $values[$idx]; }
Python
Interpreter: Python 2.5
keys = ['a', 'b', 'c'] values = [1, 2, 3] hash = dict(zip(keys, values))
Ruby
keys=['hal',666,[1,2,3]] vals=['ibm','devil',123] hash = Hash[*keys.zip(vals)] # 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.
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 }