1 files changed, 37 insertions, 0 deletions
diff --git a/823/main.py b/823/main.py
new file mode 100755
index 0000000..debdec0
--- /dev/null
+++ b/823/main.py
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# not mine
+
+from typing import List
+
+
+class Solution:
+    def __init__(self):
+        self.memo = {}
+        self.num_list = {}
+
+    def numFactoredBinaryTrees(self, arr: List[int]) -> int:
+        modulo: int = 10**9 + 7
+        N: int = len(arr)
+        arr.sort()
+        dp = [1] * N
+        index = {x: i for i, x in enumerate(arr)}
+
+        for i, x in enumerate(arr):
+            for j in range(i):
+                if x % arr[j] == 0:
+                    right = x / arr[j]
+                    if right in index:
+                        dp[i] += dp[j] * dp[int(index[int(right)])]
+                        dp[i] %= modulo
+
+        return sum(dp) % modulo
+
+
+def main():
+    solution = Solution()
+    assert solution.numFactoredBinaryTrees([2, 4]), 3
+    assert solution.numFactoredBinaryTrees([2, 4, 5, 10]), 7
+
+
+if __name__ == "__main__":
+    main()