Group Anagrams 25 XP Medium

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LeetCode #49: Group Anagrams — combines hash maps with string manipulation. A great Medium problem.

Given a list of strings, group the anagrams together. Two strings are anagrams if they have the same characters.

Example:
["eat","tea","tan","ate","nat","bat"]
→ [["eat","tea","ate"], ["tan","nat"], ["bat"]]

Key Insight: Anagrams have the same sorted character sequence. sorted('eat') = ['a','e','t'] and sorted('tea') = ['a','e','t']. Use sorted string as hash map key!

💭 Now it's your turn! Using the approach above, implement your solution in the editor. You've got this! 💪

Complexity: Time O(n · k log k) where k is max string length, Space O(n·k)

📋 Instructions

Implement `groupAnagrams(strs)` using a hash map with sorted character tuples as keys. Return a list of groups. Order within groups and order of groups doesn't matter — just group correctly.

groups = defaultdict(list). For each s in strs: key = tuple(sorted(s)), then groups[key].append(s). Return list(groups.values()). The tuple(sorted(s)) creates a hashable key that's the same for all anagrams.

⚠️ Try solving it yourself first — you'll learn more!

from collections import defaultdict

def groupAnagrams(strs):
    groups = defaultdict(list)
    for s in strs:
        key = tuple(sorted(s))   # Sorted chars as key
        groups[key].append(s)
    return list(groups.values())

🧪 Test Cases

Input

Run your code

Expected

['ate', 'eat', 'tea']
['bat']
['nat', 'tan']

Expected program output

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main.py

Hi! I'm Rex 👋

Output

Ready. Press ▶ Run or Ctrl+Enter.

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