Filter anagrams
Anagrams are words that have the same number of same letters, but in different order.
For instance:
nap - pan
ear - are - era
cheaters - hectares - teachersWrite a function aclean(arr) that returns an array cleaned from anagrams.
For instance:
let arr = ["nap", "teachers", "cheaters", "PAN", "ear", "era", "hectares"];
alert( aclean(arr) ); // "nap,teachers,ear" or "PAN,cheaters,era"From every anagram group should remain only one word, no matter which one.
To find all anagrams, let’s split every word to letters and sort them. When letter-sorted, all anagrams are same.
For instance:
nap, pan -> anp
ear, era, are -> aer
cheaters, hectares, teachers -> aceehrst
...We’ll use the letter-sorted variants as map keys to store only one value per each key:
function aclean(arr) {
let map = new Map();
for (let word of arr) {
// split the word by letters, sort them and join back
let sorted = word.toLowerCase().split('').sort().join(''); // (*)
map.set(sorted, word);
}
return Array.from(map.values());
}
let arr = ["nap", "teachers", "cheaters", "PAN", "ear", "era", "hectares"];
alert( aclean(arr) );Letter-sorting is done by the chain of calls in the line (*).
For convenience let’s split it into multiple lines:
let sorted = word // PAN
.toLowerCase() // pan
.split('') // ['p','a','n']
.sort() // ['a','n','p']
.join(''); // anpTwo different words 'PAN' and 'nap' receive the same letter-sorted form 'anp'.
The next line put the word into the map:
map.set(sorted, word);If we ever meet a word the same letter-sorted form again, then it would overwrite the previous value with the same key in the map. So we’ll always have at maximum one word per letter-form.
At the end Array.from(map.values()) takes an iterable over map values (we don’t need keys in the result) and returns an array of them.
Here we could also use a plain object instead of the Map, because keys are strings.
That’s how the solution can look:
function aclean(arr) {
let obj = {};
for (let i = 0; i < arr.length; i++) {
let sorted = arr[i].toLowerCase().split("").sort().join("");
obj[sorted] = arr[i];
}
return Object.values(obj);
}
let arr = ["nap", "teachers", "cheaters", "PAN", "ear", "era", "hectares"];
alert( aclean(arr) );