添加新题目

二叉树/从前序与中序遍历序列构造二叉树/main.go

@@ -0,0 +1,46 @@
+package main
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func main() {
+
+}
+func buildTree(preorder []int, inorder []int) *TreeNode {
+
+	var builder func(p []int, in []int) *TreeNode
+	builder = func(p []int, in []int) *TreeNode {
+		if len(in) == 0 || len(p) == 0 {
+			return nil
+		}
+		rootnum := p[0]
+		value := -1
+		for i := 0; i < len(in); i++ {
+			if in[i] == rootnum {
+				value = i
+
+			}
+		}
+		var left []int
+		var right []int
+		if value != -1 {
+			left = in[:value]
+			right = in[value+1:]
+		} else {
+			return nil
+		}
+		tmp := &TreeNode{
+			Val:   rootnum,
+			Left:  builder(p[1:1+len(left)], left),
+			Right: builder(p[1+len(left):], right),
+		}
+		return tmp
+	}
+
+	res := builder(preorder, inorder)
+
+	return res
+}