Overview

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

An anagram is a word formed by rearranging the letters of another word, using all the original letters exactly once.

Constraints

• 1 <= strs.length <= 10,000
• 0 <= strs[i].length <= 100
• strs[i] consists of lowercase English letters.
• Each group should be sorted alphabetically, and the groups themselves sorted by the first element.

Examples

groupAnagrams(["eat", "tea", "tan", "ate", "nat", "bat"]);
// => [["ate", "eat", "tea"], ["bat"], ["nat", "tan"]]

groupAnagrams([""]);
// => [[""]]

groupAnagrams(["a"]);
// => [["a"]]

Solution

function groupAnagrams(strs) {
  const map = new Map();

  for (const s of strs) {
    const key = s.split("").sort().join("");
    if (!map.has(key)) map.set(key, []);
    map.get(key).push(s);
  }

  const groups = [...map.values()];
  groups.forEach(g => g.sort());
  groups.sort((a, b) => a[0].localeCompare(b[0]));
  return groups;
}

Resources

• Group Anagrams — LeetCode
• Anagram — Wikipedia