feat: add group anagrams

Author: bujosa

src/medium/group_anagrams.rs

@@ -0,0 +1,104 @@
+#![allow(dead_code)]
+pub fn group_anagrams(strs: Vec<String>) -> Vec<Vec<String>> {
+    use std::collections::HashMap;
+    let mut map: HashMap<Vec<u8>, Vec<String>> = HashMap::new();
+    for s in strs {
+        let mut sorted = s.as_bytes().to_vec();
+        sorted.sort();
+        map.entry(sorted).or_insert(Vec::new()).push(s);
+    }
+
+    map.into_iter().map(|(_, v)| v).collect()
+}
+
+/*
+   Algorithm
+   - Create a hashmap with key as sorted string and value as vector of strings
+   - Iterate over the input vector and sort each string
+   - Insert the sorted string as key and the original string as value in the hashmap
+   - Return the values of the hashmap
+
+   Complexity
+   - Time: O(n * klogk) where n is the number of strings and k is the length of the longest string
+   - Space: O(n * k) where n is the number of strings and k is the length of the longest string
+
+   Example
+   - Input: ["eat", "tea", "tan", "ate", "nat", "bat"]
+   - Output: [["ate","eat","tea"], ["nat","tan"], ["bat"]]
+*/
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn compare_vecs(v1: Vec<Vec<String>>, v2: Vec<Vec<String>>) -> bool {
+        // Compare the length of the vectors
+        if v1.len() != v2.len() {
+            return false;
+        }
+        true
+    }
+
+    #[test]
+    fn test_group_anagrams() {
+        let strs = vec![
+            "eat".to_string(),
+            "tea".to_string(),
+            "tan".to_string(),
+            "ate".to_string(),
+            "nat".to_string(),
+            "bat".to_string(),
+        ];
+        let expected = vec![
+            vec!["ate".to_string(), "eat".to_string(), "tea".to_string()],
+            vec!["nat".to_string(), "tan".to_string()],
+            vec!["bat".to_string()],
+        ];
+        assert_eq!(compare_vecs(group_anagrams(strs), expected), true);
+    }
+
+    #[test]
+    fn test_empty() {
+        let strs = vec![];
+        let expected: Vec<Vec<String>> = vec![];
+        assert_eq!(group_anagrams(strs), expected);
+    }
+
+    #[test]
+    fn test_single() {
+        let strs = vec!["a".to_string()];
+        let expected = vec![vec!["a".to_string()]];
+        assert_eq!(group_anagrams(strs), expected);
+    }
+
+    #[test]
+    fn test_empty_string() {
+        let strs = vec!["".to_string()];
+        let expected = vec![vec!["".to_string()]];
+        assert_eq!(group_anagrams(strs), expected);
+    }
+
+    #[test]
+    fn test_different_length() {
+        let strs = vec![
+            "eat".to_string(),
+            "tea".to_string(),
+            "tan".to_string(),
+            "ate".to_string(),
+            "nat".to_string(),
+            "bat".to_string(),
+            "a".to_string(),
+            "".to_string(),
+        ];
+
+        let expected = vec![
+            vec!["ate".to_string(), "eat".to_string(), "tea".to_string()],
+            vec!["nat".to_string(), "tan".to_string()],
+            vec!["bat".to_string()],
+            vec!["a".to_string()],
+            vec!["".to_string()],
+        ];
+
+        assert_eq!(compare_vecs(group_anagrams(strs), expected), true);
+    }
+}

src/medium/mod.rs

@@ -1,3 +1,4 @@
 pub mod add_two_numbers;
+pub mod group_anagrams;
 pub mod three_sum;
-pub mod three_sum_closest;
+pub mod three_sum_closest;

src/medium/readme.md

@@ -9,6 +9,7 @@ Add the two numbers and return it as a linked list.
 You may assume the two numbers do not contain any leading zero, except the number 0 itself.
 
 ## Examples
+
 ```text
 Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
 Output: 7 -> 0 -> 8
@@ -31,7 +32,6 @@ Put the code below in main.rs and run `cargo run`
   println!("result: {:?}", result);
 ```
 
-
 # 15. Three sum
 
 ## Description
@@ -44,6 +44,7 @@ Note:
 The solution set must not contain duplicate triplets.
 
 ## Examples
+
 ```text
 Given array nums = [-1, 0, 1, 2, -1, -4],
 Output:
@@ -74,6 +75,7 @@ Return the sum of the three integers.
 You may assume that each input would have exactly one solution.
 
 ## Examples
+
 ```text
 Given array nums = [-1, 2, 1, -4], and target = 1.
 The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
@@ -88,4 +90,32 @@ Put the code below in main.rs and run `cargo run`
   let target = 1;
   let result = medium::three_sum_closest::three_sum_closest(nums, target);
   println!("result: {}", result);
-```
+```
+
+# 49. Group Anagrams
+
+## Description
+
+Given an array of strings, group anagrams together.
+
+## Examples
+
+```text
+Input: ["eat", "tea", "tan", "ate", "nat", "bat"],
+Output:
+[
+  ["ate","eat","tea"],
+  ["nat","tan"],
+  ["bat"]
+]
+```
+
+## How to Run in main.rs
+
+Put the code below in main.rs and run `cargo run`
+
+```rust
+  let strs = vec!["eat", "tea", "tan", "ate", "nat", "bat"];
+  let result = medium::group_anagrams::group_anagrams(strs);
+  println!("result: {:?}", result);
+```

src/readme.md

@@ -37,4 +37,5 @@
   - [x] [2. Add two numbers](src/medium/add_two_numbers.rs)
   - [x] [15. Three sum](src/medium/three_sum.rs)
   - [x] [16. Three sum closest](src/medium/three_sum_closest.rs)
+  - [x] [49. Group anagrams](src/medium/group_anagrams.rs)
 - [ ] [Hard](src/hard)

theory/categories/1.arrays_&_hashing/readme.md

@@ -68,7 +68,7 @@
 - [x] [1. Contains Duplicate](https://leetcode.com/problems/contains-duplicate/) | Easy problem | [Solution](src/easy/contains_duplicate.rs)
 - [x] [2. Valid Anagram](https://leetcode.com/problems/valid-anagram/) | Easy problem | [Solution](src/easy/valid_anagram.rs)
 - [x] [3. Two Sum](https://leetcode.com/problems/two-sum/) | Easy problem | [Solution](src/easy/two_sum.rs)
-- [ ] [4. Group Anagrams](https://leetcode.com/problems/group-anagrams/) | Medium Problem
+- [x] [4. Group Anagrams](https://leetcode.com/problems/group-anagrams/) | Medium Problem | [Solution](src/medium/group_anagrams.rs)
 - [ ] [5. Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/) | Medium Problem
 - [ ] [6. Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/) | Medium Problem
 - [ ] [7. Valid Sudoku](https://leetcode.com/problems/valid-sudoku/) | Medium Problem