Group Anagrams

Group Anagrams - Problem

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.

Input & Output

Example 1 — Basic Anagram Grouping

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

› Output: [["bat"],["nat","tan"],["ate","eat","tea"]]

💡 Note: eat, tea, ate contain same letters (a,e,t). tan, nat contain same letters (a,n,t). bat stands alone with letters (a,b,t).

Example 2 — Empty String

$ Input: strs = [""]

› Output: [[""]]

💡 Note: Single empty string forms one group by itself.

Example 3 — Single Character

$ Input: strs = ["a"]

› Output: [["a"]]

💡 Note: Single string with one character forms one group.

Constraints

1 ≤ strs.length ≤ 10⁴
0 ≤ strs[i].length ≤ 100
strs[i] consists of lowercase English letters only

Visualization

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Asked in

a Amazon 85 f Facebook 72 M Microsoft 68 G Google 54

The optimal approach is to sort characters in each string and use the sorted result as a hash map key. Anagrams will have identical sorted keys, allowing us to group them efficiently. Time: O(nm log m), Space: O(nm) where n is number of strings and m is average string length.

Common Approaches

✓ Optimized

⏱️ Time: N/A Space: N/A

Brute Force

⏱️ Time: O(n²m) Space: O(nm)

For each string, iterate through all other strings and check if they form anagrams by comparing character frequencies. Group matching anagrams together.

Character Frequency Count

⏱️ Time: O(nm) Space: O(nm)

Create a character frequency map for each string and use this as a signature. Strings with identical frequency maps are anagrams.

Sort Characters (Optimal)

⏱️ Time: O(nm log m) Space: O(nm)

Sort the characters of each string alphabetically. Anagrams will have identical sorted strings, which we use as keys in a hash map to group them efficiently.

Algorithm Steps — Algorithm Steps

Code -

solution.c — C

#include <stdio.h>
#include <string.h>

char* solution() {
    // C doesn't support dynamic method calls
    // Would need function pointers and complex structures
    return "Infinite method object created";
}

int main() {
    char* result = solution();
    printf("%s\n", result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

✓ Linear Growth

Space Complexity

⚡ Linearithmic Space

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High Frequency

~15 min Avg. Time

8.5K Likes

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Smart Actions

💡 Explanation

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