added 897

XianchengZ · XianchengZ · commit d6e18b5d453a · 2023-04-13T21:10:29.000-04:00
diff --git a/python/0897-all-possible-full-binary-trees.py b/python/0897-all-possible-full-binary-trees.py
@@ -0,0 +1,26 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def allPossibleFBT(self, n: int) -> List[Optional[TreeNode]]:
+        dp = { 0 : [], 1 : [ TreeNode() ] }
+
+        def backtrack(n):
+            if n in dp:
+                return dp[n]
+            
+            res = []
+            for l in range(n):
+                r = n - 1 - l
+                leftTrees, rightTrees = backtrack(l), backtrack(r)
+
+                for t1 in leftTrees:
+                    for t2 in rightTrees:
+                        res.append(TreeNode(0, t1, t2))
+            dp[n] = res
+            return res
+        
+        return backtrack(n)
