feat: add 5 more leetcode problems

Makefile

@@ -1,5 +1,5 @@
 PYTHON_VERSION = 3.13
-PROBLEM ?= reverse_nodes_in_k_group
+PROBLEM ?= number_of_connected_components_in_an_undirected_graph
 FORCE ?= 0
 COMMA := ,
 

README.md

@@ -42,11 +42,11 @@ A Python package to generate professional LeetCode practice environments. Featur
 
 - **grind-75** - Essential coding interview questions from [Grind 75](https://www.techinterviewhandbook.org/grind75/) ✅ Complete
 - **grind** - Extended Grind collection including all Grind 75 plus additional problems 🚧 Partial
-- **blind-75** - Original [Blind 75](https://leetcode.com/problem-list/xi4ci4ig/) curated list 🚧 Partial
+- **blind-75** - Original [Blind 75](https://leetcode.com/problem-list/xi4ci4ig/) curated list ✅ Complete
 - **neetcode-150** - Comprehensive [NeetCode 150](https://neetcode.io/practice) problem set 🚧 Partial
 - **algo-master-75** - Curated algorithmic mastery problems 🚧 Partial
 
-**Coverage**: 120+ unique problems across all major coding interview topics and difficulty levels.
+**Coverage**: 130+ unique problems across all major coding interview topics and difficulty levels.
 
 **Note**: Some problem sets are partially covered. We're actively working to complete all collections. [Contributions welcome!](https://github.com/wislertt/leetcode-py/blob/main/CONTRIBUTING.md)
 
@@ -82,11 +82,11 @@ lcpy gen --problem-tag neetcode-150 --output leetcode   # Generate NeetCode 150
 lcpy gen --problem-tag blind-75 --output leetcode       # Generate Blind 75 problems
 ```
 
-![Problem Generation](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/problems-generation.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/problems-generation.png" alt="Problem Generation" style="pointer-events: none;">
 
 _Bulk generation output showing "Generated problem:" messages for all 75 Grind problems_
 
-![Problem Generation 2](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/problems-generation-2.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/problems-generation-2.png" alt="Problem Generation 2" style="pointer-events: none;">
 
 _Generated folder structure showing all 75 problem directories after command execution_
 
@@ -104,19 +104,19 @@ leetcode/two_sum/
 └── __init__.py         # Package marker
 ```
 
-![README Example](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/readme-example.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/readme-example.png" alt="README Example" style="pointer-events: none;">
 
 _README format that mirrors LeetCode's problem description layout_
 
-![Solution Boilerplate](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/solution-boilerplate.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/solution-boilerplate.png" alt="Solution Boilerplate" style="pointer-events: none;">
 
 _Solution boilerplate with type hints and TODO placeholder_
 
-![Test Example](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/test-example.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/test-example.png" alt="Test Example" style="pointer-events: none;">
 
 _Comprehensive parametrized tests with 10+ test cases - executable and debuggable in local development environment_
 
-![Test Logging](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/logs-in-test-solution.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/logs-in-test-solution.png" alt="Test Logging" style="pointer-events: none;">
 
 _Beautiful colorful test output with loguru integration for enhanced debugging and test result visualization_
 
@@ -141,21 +141,21 @@ Professional-grade visualization for debugging complex data structures with dual
 
 #### Jupyter Notebook Integration (HTML Rendering)
 
-![Tree Visualization](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/tree-viz.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/tree-viz.png" alt="Tree Visualization" style="pointer-events: none;">
 
 _Interactive tree visualization using Graphviz SVG rendering in Jupyter notebooks_
 
-![LinkedList Visualization](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/linkedlist-viz.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/linkedlist-viz.png" alt="LinkedList Visualization" style="pointer-events: none;">
 
 _Professional linked list visualization with Graphviz in Jupyter environment_
 
 #### Terminal/Console Output (String Rendering)
 
-![Tree String Visualization](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/tree-str-viz.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/tree-str-viz.png" alt="Tree String Visualization" style="pointer-events: none;">
 
 _Clean ASCII tree rendering using anytree for terminal debugging and logging_
 
-![LinkedList String Visualization](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/linkedlist-str-viz.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/linkedlist-str-viz.png" alt="LinkedList String Visualization" style="pointer-events: none;">
 
 _Simple arrow-based list representation for console output and test debugging_
 
@@ -166,7 +166,7 @@ _Simple arrow-based list representation for console output and test debugging_
 - **Repository State**: This repo converts them to Python files (`.py`) for better version control
 - **Dual Rendering**: Automatic HTML visualization in notebooks, clean string output in terminals
 
-![Notebook Example](https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/notebook-example.png)
+<img src="https://raw.githubusercontent.com/wislertt/leetcode-py/main/docs/images/notebook-example.png" alt="Notebook Example" style="pointer-events: none;">
 
 _Interactive multi-cell playground with rich data structure visualization for each problem_
 
@@ -301,8 +301,8 @@ make gen-all-problems              # Regenerate all problems (destructive)
 
 ## 🏗️ Architecture
 
-- **Template-Driven**: JSON templates in `.templates/leetcode/json/` drive code generation
-- **Cookiecutter Integration**: Uses `.templates/leetcode/{{cookiecutter.problem_name}}/` template for consistent file structure
+- **Template-Driven**: JSON templates in `leetcode_py/cli/resources/leetcode/json/problems/` drive code generation
+- **Cookiecutter Integration**: Uses `leetcode_py/cli/resources/leetcode/{{cookiecutter.problem_name}}/` template for consistent file structure
 - **Automated Scraping**: LLM-assisted problem data extraction from LeetCode
 - **Version Control Friendly**: Python files by default, optional notebook support
 

docs/cli-usage.md

@@ -187,7 +187,7 @@ Available tags for bulk operations:
 
 - `grind-75` - Essential 75 coding interview problems from [Grind 75](https://www.techinterviewhandbook.org/grind75/) ✅ Complete
 - `grind` - Extended Grind collection (100+ problems) including all Grind 75 plus additional problems 🚧 Partial
-- `blind-75` - Original [Blind 75](https://leetcode.com/discuss/general-discussion/460599/blind-75-leetcode-questions) curated list 🚧 Partial
+- `blind-75` - Original [Blind 75](https://leetcode.com/discuss/general-discussion/460599/blind-75-leetcode-questions) curated list ✅ Complete
 - `neetcode-150` - Comprehensive [NeetCode 150](https://neetcode.io/practice) problem set (150+ problems) 🚧 Partial
 - `algo-master-75` - Curated algorithmic mastery problems (75 problems) 🚧 Partial
 

leetcode/encode_and_decode_strings/README.md

@@ -0,0 +1,39 @@
+# Encode and Decode Strings
+
+**Difficulty:** Medium
+**Topics:** Array, String, Design
+**Tags:** blind-75
+
+**LeetCode:** [Problem 271](https://leetcode.com/problems/encode-and-decode-strings/description/)
+
+## Problem Description
+
+Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.
+
+## Examples
+
+### Example 1:
+
+```
+Input: dummy_input = ["Hello","World"]
+Output: "Hello,World"
+Explanation: Machine 1:
+Codec encoder = new Codec();
+String msg = encoder.encode(strs);
+Machine 1 ---msg---> Machine 2
+Machine 2:
+Codec decoder = new Codec();
+String[] strs = decoder.decode(msg);
+```
+
+## Constraints
+
+- 1 <= strs.length <= 200
+- 0 <= strs[i].length <= 200
+- strs[i] contains any possible characters out of 256 valid ASCII characters.
+
+**Note:**
+
+- The string may contain any possible characters out of 256 valid ASCII characters. Your algorithm should be generalized enough to work on any possible characters.
+- Do not use class member/global/static variables to store states. Your encode and decode algorithms should be stateless.
+- Do not rely on any library method such as eval or serialize methods. You should implement your own encode/decode algorithm.

leetcode/encode_and_decode_strings/helpers.py

@@ -0,0 +1,10 @@
+def run_encode_decode(solution_class: type, strs: list[str]):
+    implementation = solution_class()
+    encoded = implementation.encode(strs)
+    decoded = implementation.decode(encoded)
+    return decoded
+
+
+def assert_encode_decode(result: list[str], expected: list[str]) -> bool:
+    assert result == expected
+    return True

leetcode/encode_and_decode_strings/playground.py

@@ -0,0 +1,29 @@
+# ---
+# jupyter:
+#   jupytext:
+#     text_representation:
+#       extension: .py
+#       format_name: percent
+#       format_version: '1.3'
+#       jupytext_version: 1.17.3
+#   kernelspec:
+#     display_name: leetcode-py-py3.13
+#     language: python
+#     name: python3
+# ---
+
+# %%
+from helpers import assert_encode_decode, run_encode_decode
+from solution import Solution
+
+# %%
+# Example test case
+strs = ["Hello", "World"]
+expected = strs
+
+# %%
+result = run_encode_decode(Solution, strs)
+result
+
+# %%
+assert_encode_decode(result, expected)

leetcode/encode_and_decode_strings/solution.py

@@ -0,0 +1,33 @@
+class Solution:
+
+    # Time: O(n)
+    # Space: O(n)
+    def encode(self, strs: list[str]) -> str:
+        encoded = ""
+        for s in strs:
+            # Format: length + '#' + string
+            encoded += str(len(s)) + "#" + s
+        return encoded
+
+    # Time: O(n)
+    # Space: O(n)
+    def decode(self, s: str) -> list[str]:
+        decoded = []
+        i = 0
+
+        while i < len(s):
+            # Find the delimiter '#'
+            j = i
+            while s[j] != "#":
+                j += 1
+
+            # Extract length
+            length = int(s[i:j])
+
+            # Extract string of that length
+            decoded.append(s[j + 1 : j + 1 + length])
+
+            # Move to next encoded string
+            i = j + 1 + length
+
+        return decoded

leetcode/encode_and_decode_strings/test_solution.py

@@ -0,0 +1,41 @@
+import pytest
+
+from leetcode_py import logged_test
+
+from .helpers import assert_encode_decode, run_encode_decode
+from .solution import Solution
+
+
+class TestEncodeAndDecodeStrings:
+    def setup_method(self):
+        self.solution = Solution()
+
+    @logged_test
+    @pytest.mark.parametrize(
+        "strs",
+        [
+            ["Hello", "World"],
+            ["abc", "def"],
+            [""],
+            ["a", "b", "c"],
+            ["", "", ""],
+            ["hello", "", "world"],
+            ["a#b", "c#d"],
+            ["4#3hello", "world"],
+            ["#", "##", "###"],
+            ["abc123", "def456", "ghi789"],
+            ["special!@#$%^&*()"],
+            ["with spaces", "and tabs\t", "and newlines\n"],
+            ["unicode测试", "emoji😀"],
+            ["very long string " * 10],
+            ["a" * 200],
+            [],
+            ["single"],
+            ["comma,separated", "values,here"],
+            ["pipe|separated", "values|here"],
+            ["colon:separated", "values:here"],
+        ],
+    )
+    def test_encode_decode(self, strs: list[str]):
+        result = run_encode_decode(Solution, strs)
+        assert_encode_decode(result, strs)

leetcode/graph_valid_tree/README.md

@@ -0,0 +1,38 @@
+# Graph Valid Tree
+
+**Difficulty:** Medium
+**Topics:** Depth-First Search, Breadth-First Search, Union Find, Graph
+**Tags:** blind-75
+
+**LeetCode:** [Problem 261](https://leetcode.com/problems/graph-valid-tree/description/)
+
+## Problem Description
+
+Given `n` nodes labeled from `0` to `n-1` and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree.
+
+## Examples
+
+### Example 1:
+
+```
+Input: n = 5, and edges = [[0,1], [0,2], [0,3], [1,4]]
+Output: true
+```
+
+### Example 2:
+
+```
+Input: n = 5, and edges = [[0,1], [1,2], [2,3], [1,3], [1,4]]
+Output: false
+```
+
+## Constraints
+
+- 0 <= n <= 2000
+- 0 <= edges.length <= 5000
+- edges[i].length == 2
+- 0 <= ai, bi < n
+- ai != bi
+- There are no self-loops or repeated edges.
+
+**Note:** you can assume that no duplicate edges will appear in edges. Since all edges are undirected, [0,1] is the same as [1,0] and thus will not appear together in edges.

leetcode/graph_valid_tree/helpers.py

@@ -0,0 +1,8 @@
+def run_valid_tree(solution_class: type, n: int, edges: list[list[int]]):
+    implementation = solution_class()
+    return implementation.valid_tree(n, edges)
+
+
+def assert_valid_tree(result: bool, expected: bool) -> bool:
+    assert result == expected
+    return True

leetcode/graph_valid_tree/playground.py

@@ -0,0 +1,30 @@
+# ---
+# jupyter:
+#   jupytext:
+#     text_representation:
+#       extension: .py
+#       format_name: percent
+#       format_version: '1.3'
+#       jupytext_version: 1.17.3
+#   kernelspec:
+#     display_name: leetcode-py-py3.13
+#     language: python
+#     name: python3
+# ---
+
+# %%
+from helpers import assert_valid_tree, run_valid_tree
+from solution import Solution
+
+# %%
+# Example test case
+n = 5
+edges = [[0, 1], [0, 2], [0, 3], [1, 4]]
+expected = True
+
+# %%
+result = run_valid_tree(Solution, n, edges)
+result
+
+# %%
+assert_valid_tree(result, expected)

leetcode/graph_valid_tree/solution.py

@@ -0,0 +1,33 @@
+class Solution:
+
+    # Time: O(n + e)
+    # Space: O(n + e)
+    def valid_tree(self, n: int, edges: list[list[int]]) -> bool:
+        # Edge case: empty graph is a valid tree
+        if n == 0:
+            return True
+
+        # A valid tree must have exactly n-1 edges
+        if len(edges) != n - 1:
+            return False
+
+        # Build adjacency list
+        graph: list[list[int]] = [[] for _ in range(n)]
+        for u, v in edges:
+            graph[u].append(v)
+            graph[v].append(u)
+
+        # DFS to check connectivity
+        visited = set()
+
+        def dfs(node: int) -> None:
+            visited.add(node)
+            for neighbor in graph[node]:
+                if neighbor not in visited:
+                    dfs(neighbor)
+
+        # Start DFS from node 0
+        dfs(0)
+
+        # Check if all nodes are visited (connected)
+        return len(visited) == n