From 39a357bd3917bff0479fb0760007c7c970a66bfb Mon Sep 17 00:00:00 2001
From: Siddhartha Dutta <siddharthadutta@protonmail.com>
Date: Sun, 29 Dec 2024 15:22:33 +0000
Subject: [PATCH] Dec 29

---
 ...Form a Target String Given a Dictionary.py | 35 +++++++++++++++++++
 .../README.md                                 |  6 ++--
 2 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 2024-12-December-LeetCoding-Challenge/Number of Ways to Form a Target String Given a Dictionary.py

diff --git a/2024-12-December-LeetCoding-Challenge/Number of Ways to Form a Target String Given a Dictionary.py b/2024-12-December-LeetCoding-Challenge/Number of Ways to Form a Target String Given a Dictionary.py
new file mode 100644
index 0000000..39eebfc
--- /dev/null
+++ b/2024-12-December-LeetCoding-Challenge/Number of Ways to Form a Target String Given a Dictionary.py	
@@ -0,0 +1,35 @@
+from collections import Counter
+from functools import lru_cache
+from typing import List
+
+
+class Solution:
+    def numWays(self, words: List[str], target: str) -> int:
+        count = [Counter() for _ in range(len(words[0]))]
+        for word in words:
+            for idx, ch in enumerate(word):
+                count[idx][ch] += 1
+
+        @lru_cache(None)
+        def dfs(i: int = 0, j: int = 0) -> int:
+            if i == len(target):
+                return 1
+            if j == len(words[0]):
+                return 0
+            return (dfs(i, j+1) + dfs(i+1, j+1) * count[j][target[i]]) % int(1e9 + 7)
+
+        return dfs()
+
+
+def main():
+    words = ['acca', 'bbbb', 'caca']
+    target = 'aba'
+    assert Solution().numWays(words, target) == 6
+
+    words = ['abba', 'baab']
+    target = 'bab'
+    assert Solution().numWays(words, target) == 4
+
+
+if __name__ == '__main__':
+    main()
diff --git a/2024-12-December-LeetCoding-Challenge/README.md b/2024-12-December-LeetCoding-Challenge/README.md
index ec8c166..b69d7bc 100644
--- a/2024-12-December-LeetCoding-Challenge/README.md
+++ b/2024-12-December-LeetCoding-Challenge/README.md
@@ -30,8 +30,8 @@
 | December 25 | [515. Find Largest Value in Each Tree Row](https://leetcode.com/problems/find-largest-value-in-each-tree-row/) | Medium | Solved |
 | December 26 | [494. Target Sum](https://leetcode.com/problems/target-sum/) | Medium | Solved |
 | December 27 | [1014. Best Sightseeing Pair](https://leetcode.com/problems/best-sightseeing-pair/) | Medium | Unsolved |
-| December 28 | []() |  |  |
-| December 29 | []() |  |  |
+| December 28 | [689. Maximum Sum of 3 Non-Overlapping Subarrays](https://leetcode.com/problems/maximum-sum-of-3-non-overlapping-subarrays/) | Hard | Unsolved |
+| December 29 | [1639. Number of Ways to Form a Target String Given a Dictionary](https://leetcode.com/problems/number-of-ways-to-form-a-target-string-given-a-dictionary/) | Hard | Unsolved |
 | December 30 | []() |  |  |
 | December 31 | []() |  |  |
 
@@ -40,4 +40,4 @@
 | ---    | --- | --- | --- |
 | Easy   | 5 | 5 | 0 |
 | Medium | 19 | 12 | 7 |
-| Hard   | 3 | 0 | 3 |
+| Hard   | 5 | 0 | 5 |