105 树结构

Author: baxiang

105construct-binary-tree-from-preorder-and-inorder-traversal/main.go

@@ -0,0 +1,53 @@
+package main
+
+import "fmt"
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func buildTree(preorder []int, inorder []int) *TreeNode {
+	if len(preorder) == 0 {
+		return nil
+	}
+	rootVal := preorder[0]
+	i := 0
+	// 查找根节点位置
+	for ; i < len(inorder); i++ {
+		if rootVal == inorder[i] {
+			break
+		}
+	}
+	root := &TreeNode{Val: rootVal}
+	root.Left = buildTree(preorder[1:i+1], inorder[:i])
+	root.Right = buildTree(preorder[i+1:], inorder[i+1:])
+	return root
+}
+
+func main() {
+	r := buildTree([]int{3, 9, 20, 15, 7}, []int{9, 3, 15, 20, 7})
+	printPreorder(r)
+	fmt.Println()
+	printInorder(r)
+
+}
+func printPreorder(r *TreeNode) {
+	if r == nil {
+		return
+	}
+	fmt.Print(r.Val)
+	printPreorder(r.Left)
+	printPreorder(r.Right)
+}
+
+func printInorder(r *TreeNode) {
+	if r == nil {
+		return
+	}
+
+	printInorder(r.Left)
+	fmt.Print(r.Val)
+	printInorder(r.Right)
+}