【Arai60】29問目 105. Construct Binary Tree from Preorder and Inorder Traversal

arai60/21-29_Tree_BT_BST/29_105_Construct Binary Tree from Preorder and Inorder Traversal/level_1.py

@@ -0,0 +1,21 @@
+class Solution:
+    def buildTree(
+        self, preorder: List[int], inorder: List[int]
+    ) -> Optional[TreeNode]:
+        current_preorder_index = 0
+
+        def array_to_tree(split_inorder):
+            nonlocal current_preorder_index
+            if current_preorder_index >= len(preorder):
+                return None
+            val = preorder[current_preorder_index]
+            if not val in split_inorder:
+                return None
+            current_preorder_index += 1
+            node = TreeNode(val)
+            inorder_index = split_inorder.index(val)
+            node.left = array_to_tree(split_inorder[:inorder_index])
+            node.right = array_to_tree(split_inorder[inorder_index + 1 :])
+            return node
+
+        return array_to_tree(inorder)

arai60/21-29_Tree_BT_BST/29_105_Construct Binary Tree from Preorder and Inorder Traversal/level_2.py

@@ -0,0 +1,24 @@
+# 再帰関数の引数をinorderのindexで管理
+class Solution:
+    def buildTree(
+        self, preorder: List[int], inorder: List[int]
+    ) -> Optional[TreeNode]:
+        inorder_index_map = {}
+        for i, val in enumerate(inorder):
+            inorder_index_map[val] = i
+
+        current_preorder_index = 0
+
+        def array_to_tree(inorder_left, inorder_right):
+            nonlocal current_preorder_index
+            if inorder_left > inorder_right:
+                return None
+            val = preorder[current_preorder_index]
+            node = TreeNode(val)
+            inorder_index = inorder_index_map[val]
+            current_preorder_index += 1
+            node.left = array_to_tree(inorder_left, inorder_index - 1)
+            node.right = array_to_tree(inorder_index + 1, inorder_right)
+            return node
+
+        return array_to_tree(0, len(inorder) - 1)

arai60/21-29_Tree_BT_BST/29_105_Construct Binary Tree from Preorder and Inorder Traversal/level_3.py

@@ -0,0 +1,23 @@
+class Solution:
+    def buildTree(
+        self, preorder: List[int], inorder: List[int]
+    ) -> Optional[TreeNode]:
+        inorder_index_map = {}
+        for i, val in enumerate(inorder):
+            inorder_index_map[val] = i
+
+        current_preorder_index = 0
+
+        def array_to_tree(inorder_left, inorder_right):
+            nonlocal current_preorder_index
+            if inorder_left > inorder_right:
+                return None
+            val = preorder[current_preorder_index]
+            node = TreeNode(val)
+            inorder_index = inorder_index_map[val]
+            current_preorder_index += 1
+            node.left = array_to_tree(inorder_left, inorder_index - 1)
+            node.right = array_to_tree(inorder_index + 1, inorder_right)
+            return node
+
+        return array_to_tree(0, len(inorder) - 1)

arai60/21-29_Tree_BT_BST/29_105_Construct Binary Tree from Preorder and Inorder Traversal/level_4.py

@@ -0,0 +1,24 @@
+#  [inorder_left, inorder_right) 右側を開区間に修正
+class Solution:
+    def buildTree(
+        self, preorder: List[int], inorder: List[int]
+    ) -> Optional[TreeNode]:
+        inorder_index_map = {}
+        for i, val in enumerate(inorder):
+            inorder_index_map[val] = i
+
+        current_preorder_index = 0
+
+        def array_to_tree(inorder_left, inorder_right):
+            nonlocal current_preorder_index
+            if inorder_left >= inorder_right:
+                return None
+            val = preorder[current_preorder_index]
+            node = TreeNode(val)
+            inorder_index = inorder_index_map[val]
+            current_preorder_index += 1
+            node.left = array_to_tree(inorder_left, inorder_index)
+            node.right = array_to_tree(inorder_index + 1, inorder_right)
+            return node
+
+        return array_to_tree(0, len(inorder))