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Programming-Idioms

  • Haskell
  • Dart

Idiom #113 Iterate over map entries, ordered by values

Print each key k with its value x from an associative array mymap, in ascending order of x.
Multiple entries may exist for the same value x.

mymap.entries.toList()
    ..sort((a, b) => a.value.compareTo(b.value))
    ..forEach(print);
import Data.Map as Map
import Data.List (sortOn)
mapM_ print . sortOn snd $ Map.toList mymap

Using Map.toList to convert the map to a list of (key, value) pairs, then sort the list based on the second element of the pair with sortOn snd.
import Data.Map as Map
import Data.List (sortBy)
import Data.Ord (comparing)
mapM_ print $ sortBy (comparing snd) $ Map.toList mymap

Map.toList gives a list of all (key,value) pairs. Sorts on the values (second item of the pairs) and prints.

$ is apply operator and serves here only to save parentheses.
for_each(begin(mymap), end(mymap),
    [&s](const auto& kv) { s.insert(kv.second); });

Using a std::multiset<>
New implementation...
< > ⌨
programming-idioms.org 
mymap.entries.toList()
    ..sort((a, b) => a.value.compareTo(b.value))
    ..forEach(print);
mapM_ print . sortOn snd $ Map.toList mymap
mapM_ print $ sortBy (comparing snd) $ Map.toList mymap
for_each(begin(mymap), end(mymap),
    [&s](const auto& kv) { s.insert(kv.second); });
Dictionary<String, String> mymap = new Dictionary<String, String>();
  
foreach(KeyValuePair<string, string> a in mymap.OrderBy(x => x.Value))
{
  Console.WriteLine("Key = {0}, Value = {1}", a.Key, a.Value);
}
mymap.byKeyValue
     .array
     .sort!((a, b) => a.value < b.value)
     .each!(p => writeln(p.key, " ", p.value));

mymap 
|> Map.to_list 
|> Enum.sort(fn ({_k1, val1}, {_k2, val2}) -> val1 <= val2 end)
|> Enum.each(fn ({k, v}) -> IO.puts("#{k}: #{v}") end)
type entry struct {
	key   string
	value int
}

entries := make([]entry, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, value: x})
}
sort.Slice(entries, func(i, j int) bool {
	return entries[i].value < entries[j].value
})

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
type entry struct {
	key   string
	value int
}

type entries []entry
func (list entries) Len() int { return len(list) }
func (list entries) Less(i, j int) bool { return list[i].value < list[j].value }
func (list entries) Swap(i, j int) { list[i], list[j] = list[j], list[i] }

entries := make(entries, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, values: x})
}
sort.Sort(entries)

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
Object.entries(mymap)
  .sort((a, b) => a[1] - b[1])
  .forEach(([key, value]) => {
    console.log('key:', key, 'value:', value);
  });
mymap.entrySet().stream()
    .sorted(Comparator.comparing(Map.Entry::getValue))
    .forEach(entry -> {
        K k = entry.getKey();
        X x = entry.getValue();
        System.out.println("k:" + k + ", x:" + x);
});


mymap.entrySet()
    .stream()
    .sorted(comparingByValue())
    .forEach(out::println);
mymap.entrySet()
    .stream()
    .sorted(comparingByValue())
    .forEach(e -> {
        K k = e.getKey();
        X x = e.getValue();
    });
for my $k (sort {($mymap{$a}<=>$mymap{$b}) or ($a cmp $b)}
           keys %mymap) {
   print "$k: $mymap{$k}\n";
}
sub by_val_then_key {
    return ($mymap{$a} <=> $mymap{$b})
        or ($a cmp $b)
}

for my $k (sort by_val_then_key keys %mymap) {
   print "$k: $mymap{$k}\n";
}


dict_pairs(D, _, Ps),
transpose_pairs(Ps, TPs),
keysort(TPs, Val_sorted),
forall(member(V-K, Val_sorted),
       format("~w:~w~n", [V, K]))
for key, value in sorted(d.items(), key=operator.itemgetter(1)):
    print(key, value)
for x, k in sorted((x, k) for k,x in mymap.items()):
    print(k, x)

for x in sorted(mymap.items(), key=itemgetter(1)):
    print(x)
for x in sorted(mymap, key=mymap.get):
    print(x, mymap[x])
mymap.sort_by{|k,x| x}.each{|k,x| puts "#{k}: #{x}"}
let mut items: Vec<_> = mymap.iter().collect();
items.sort_by_key(|item| item.1);
for (k, x) in items {
    println!("[{},{}]", k, x);
}
for (k, x) in mymap.iter().sorted_by_key(|x| x.1) {
	println!("[{},{}]", k, x);
}