Leetcode Algorithm

49. Group Anagrams

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

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.

Example 1:

Input: strs = ["eat","tea","tan","ate","nat","bat"]
Output: [["bat"],["nat","tan"],["ate","eat","tea"]]

Example 2:

Input: strs = [""]
Output: [[""]]

Example 3:

Input: strs = ["a"]
Output: [["a"]]

Constraints:

• 1 <= strs.length <= 104
• 0 <= strs[i].length <= 100
• strs[i] consists of lower-case English letters.

Solution:

## categorize by sorted string
class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        ans = collections.defaultdict(list)
        for s in range(strs):
            ans[tuple(sorted(s))].append(s)
        return ans.values()

TC: O(NKlogK)

SC: O(NK)

## categorize by count
class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        ans = collections.defaultdict(list)
        for s in strs:
            count = [0] * 26
            for c in s: # each letter in s
                count[ord(c) - ord('a')] += 1
            ans[tuple(count)].append(s)
        return ans.values()

TC: O(NK)

SC:(NK)

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