feat: monday

pkg/construct_binary_tree_from_preorder_and_inorder_traversal/main.go

@@ -0,0 +1,65 @@
+package constructbinarytreefrompreorderandinordertraversal
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+type NodeInfo struct {
+	Val      int
+	Preorder int
+	Inorder  int
+}
+
+func buildTreeInfo(info []NodeInfo) *TreeNode {
+	if len(info) == 0 {
+		return nil
+	}
+
+	root_info := info[0]
+	for _, datum := range info {
+		if datum.Preorder < root_info.Preorder {
+			root_info = datum
+		}
+	}
+
+	left_info := []NodeInfo{}
+	right_info := []NodeInfo{}
+	for _, datum := range info {
+		if datum.Inorder < root_info.Inorder {
+			left_info = append(left_info, datum)
+		} else if datum.Inorder > root_info.Inorder {
+			right_info = append(right_info, datum)
+		} else {
+			continue
+		}
+	}
+
+	return &TreeNode{
+		Val:   root_info.Val,
+		Left:  buildTreeInfo(left_info),
+		Right: buildTreeInfo(right_info),
+	}
+}
+
+func buildTree(preorder []int, inorder []int) *TreeNode {
+	info_map := map[int]*NodeInfo{}
+	for o, v := range preorder {
+		info_map[v] = &NodeInfo{
+			Val:      v,
+			Preorder: o,
+		}
+	}
+
+	for o, v := range inorder {
+		info_map[v].Inorder = o
+	}
+
+	info := []NodeInfo{}
+	for _, datum := range info_map {
+		info = append(info, *datum)
+	}
+
+	return buildTreeInfo(info)
+}