May 09

Author: siddydutta

2025-05-May-LeetCoding-Challenge/Count Number of Balanced Permutations.py

@@ -0,0 +1,42 @@
+from functools import lru_cache
+from collections import Counter
+from math import comb
+
+
+class Solution:
+    MOD = 10**9 + 7
+
+    def countBalancedPermutations(self, num: str) -> int:
+        count = Counter(map(int, num))
+        total = sum(map(int, num))
+
+        @lru_cache(None)
+        def dfs(i: int, odd: int, even: int, balance: int) -> int:
+            if odd == 0 and even == 0 and balance == 0:
+                return 1
+            if i < 0 or odd < 0 or even < 0 or balance < 0:
+                return 0
+
+            res = 0
+            for j in range(0, count[i] + 1):
+                res += comb(odd, j) * \
+                    comb(even, count[i] - j) * \
+                    dfs(i - 1, odd - j, even - count[i] + j, balance - i * j)
+            return res % self.MOD
+
+        return 0 if total % 2 else dfs(9, len(num) - len(num) // 2, len(num) // 2, total // 2)
+
+
+def main():
+    num = '123'
+    assert Solution().countBalancedPermutations(num) == 2
+
+    num = '112'
+    assert Solution().countBalancedPermutations(num) == 1
+
+    num = '12345'
+    assert Solution().countBalancedPermutations(num) == 0
+
+
+if __name__ == '__main__':
+    main()

2025-05-May-LeetCoding-Challenge/README.md

@@ -12,7 +12,7 @@
 | May 06 | [1920. Build Array from Permutation](https://leetcode.com/problems/build-array-from-permutation/) | Easy | Solved |
 | May 07 | [3341. Find Minimum Time to Reach Last Room I](https://leetcode.com/problems/find-minimum-time-to-reach-last-room-i/) | Medium | Solved |
 | May 08 | [3342. Find Minimum Time to Reach Last Room II](https://leetcode.com/problems/find-minimum-time-to-reach-last-room-ii/) | Medium | Solved |
-| May 09 | []() |  |  |
+| May 09 | [3343. Count Number of Balanced Permutations](https://leetcode.com/problems/count-number-of-balanced-permutations/) | Hard | Unsolved |
 | May 10 | []() |  |  |
 | May 11 | []() |  |  |
 | May 12 | []() |  |  |
@@ -42,4 +42,4 @@
 | ---    | --- | --- | --- |
 | Easy   | 2 | 2 | 0 |
 | Medium | 5 | 5 | 0 |
-| Hard   | 1 | 1 | 0 |
+| Hard   | 2 | 1 | 1 |