105 accepted. 52ms. The Fastest is 38ms.

Author: aQua

Algorithms/0105.construct-binary-tree-from-preorder-and-inorder-traversal/README.md

@@ -3,7 +3,7 @@
 ## 题目
 Given preorder and inorder traversal of a tree, construct the binary tree.
 
-Note:
+**Note:**
 You may assume that duplicates do not exist in the tree.
 
 ## 解题思路

Algorithms/0105.construct-binary-tree-from-preorder-and-inorder-traversal/construct-binary-tree-from-preorder-and-inorder-traversal.go

@@ -1,5 +1,37 @@
 package Problem0105
+import (
+	"github.com/aQuaYi/LeetCode-in-Golang/kit"
+)
+type TreeNode = kit.TreeNode
 
-func buildTree(preorder []int, inorder []int) *TreeNode {
+func buildTree(pre, in []int) *TreeNode {
 
+	if len(in) == 0 {
+		return nil
+	}
+
+	res := &TreeNode{
+		Val: pre[0],
+	}
+
+	if len(in) == 1 {
+		return res
+	}
+
+	idx := indexOf(res.Val, in)
+
+	res.Left = buildTree(pre[1:idx+1], in[:idx])
+	res.Right = buildTree(pre[idx+1:], in[idx+1:])
+
+	return res
+}
+
+func indexOf(val int, nums []int) int {
+	for i, v := range nums {
+		if v == val {
+			return i
+		}
+	}
+
+	return 0
 }

Algorithms/0105.construct-binary-tree-from-preorder-and-inorder-traversal/construct-binary-tree-from-preorder-and-inorder-traversal_test.go

@@ -1,8 +1,10 @@
 package Problem0105
 
 import (
-	"testing"
 	"fmt"
+	"testing"
+
+	"github.com/aQuaYi/LeetCode-in-Golang/kit"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -15,12 +17,12 @@ type question struct {
 // para 是参数
 type para struct {
 	preorder []int
- inorder []int
+	inorder  []int
 }
 
 // ans 是答案
 type ans struct {
-	one  *TreeNode 
+	postorder []int
 }
 
 func Test_Problem0105(t *testing.T) {
@@ -30,20 +32,21 @@ func Test_Problem0105(t *testing.T) {
 
 		question{
 			para{
-					,
+				[]int{1, 2, 4, 5, 3, 6, 7},
+				[]int{4, 2, 5, 1, 6, 3, 7},
 			},
 			ans{
-					,
+				[]int{4, 5, 2, 6, 7, 3, 1},
 			},
 		},
-	
+
 		// 如需多个测试，可以复制上方元素。
 	}
 
 	for _, q := range qs {
 		a, p := q.ans, q.para
 		fmt.Printf("~~%v~~\n", p)
 
-		ast.Equal(a.one, buildTree(p.  ), "输入:%v", p)
+		ast.Equal(a.postorder, kit.Tree2Postorder(buildTree(p.preorder, p.inorder)), "输入:%v", p)
 	}
 }