Feb 19

Author: siddydutta

2025-02-February-LeetCoding-Challenge/README.md

@@ -22,7 +22,7 @@
 | February 16 | [1718. Construct the Lexicographically Largest Valid Sequence](https://leetcode.com/problems/construct-the-lexicographically-largest-valid-sequence/) | Medium | Unsolved |
 | February 17 | [1079. Letter Tile Possibilities](https://leetcode.com/problems/letter-tile-possibilities/) | Medium | Solved |
 | February 18 | [2375. Construct Smallest Number From DI String](https://leetcode.com/problems/construct-smallest-number-from-di-string/) | Medium | Unsolved |
-| February 19 | []() |  |  |
+| February 19 | [1415. The k-th Lexicographical String of All Happy Strings of Length n](https://leetcode.com/problems/the-k-th-lexicographical-string-of-all-happy-strings-of-length-n/) | Medium | Unsolved |
 | February 20 | []() |  |  |
 | February 21 | []() |  |  |
 | February 22 | []() |  |  |
@@ -38,5 +38,5 @@
 | Level  | Problems | Solved | Unsolved |
 | ---    | --- | --- | --- |
 | Easy   | 6 | 6 | 0 |
-| Medium | 11 | 9 | 2 |
+| Medium | 12 | 9 | 3 |
 | Hard   | 0 | 0 | 0 |

2025-02-February-LeetCoding-Challenge/The k-th Lexicographical String of All Happy Strings of Length n.py

@@ -0,0 +1,30 @@
+from collections import deque
+
+
+class Solution:
+    def getHappyString(self, n: int, k: int) -> str:
+        next_map = {'a': 'bc', 'b': 'ac', 'c': 'ab'}
+        queue = deque(next_map.keys())
+        while len(queue[0]) != n:
+            u = queue.popleft()
+            for v in next_map[u[-1]]:
+                queue.append(u + v)
+        return queue[k-1] if len(queue) >= k else ''
+
+
+def main():
+    n = 1
+    k = 3
+    assert Solution().getHappyString(n, k) == 'c'
+
+    n = 1
+    k = 4
+    assert Solution().getHappyString(n, k) == ''
+
+    n = 3
+    k = 9
+    assert Solution().getHappyString(n, k) == 'cab'
+
+
+if __name__ == '__main__':
+    main()