feat(solutions): add binary_tree_inorder_traversal

Author: WindomZ

README.md

@@ -33,6 +33,7 @@
 
 | # | **Problem** & **Solution** | Difficulty | Single Repetition Duration | LeetCode Run Time |
 | ---: | :----- | :----------: | ----------: | ----------: |
+|[94][Solutions-94]|[Binary Tree Inorder Traversal][Solutions-94-Home]|Medium|[119 ns/op][Solutions-94-Code] / [3 test cases][Solutions-94-Test]|0 ms|
 |[93][Solutions-93]|[Restore IP Addresses][Solutions-93-Home]|Medium|[251 ns/op][Solutions-93-Code] / [4 test cases][Solutions-93-Test]|4 ms|
 |[92][Solutions-92]|[Reverse Linked List II][Solutions-92-Home]|Medium|[61.5 ns/op][Solutions-92-Code] / [3 test cases][Solutions-92-Test]|3 ms|
 |[91][Solutions-91]|[Decode Ways][Solutions-91-Home]|Medium|[68.3 ns/op][Solutions-91-Code] / [8 test cases][Solutions-91-Test]|3 ms|
@@ -149,6 +150,10 @@ Welcome to report bugs, suggest ideas and discuss on [issues page](https://githu
 ### Support
 If you like it then you can put a :star:Star on it.
 
+[Solutions-94]:https://leetcode.com/problems/binary-tree-inorder-traversal/
+[Solutions-94-Home]:solutions/binary_tree_inorder_traversal/
+[Solutions-94-Code]:solutions/binary_tree_inorder_traversal/binarytreeinordertraversal.go
+[Solutions-94-Test]:solutions/binary_tree_inorder_traversal/binarytreeinordertraversal_test.go#L49
 [Solutions-93]:https://leetcode.com/problems/restore-ip-addresses/
 [Solutions-93-Home]:solutions/restore_ip_addresses/
 [Solutions-93-Code]:solutions/restore_ip_addresses/restoreipaddresses.go

solutions/binary_tree_inorder_traversal/NOTE_Ch-zh.md

@@ -0,0 +1,27 @@
+# [94. Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/description/)
+
+## Description
+
+Given a binary tree, return the _inorder_ traversal of its nodes' values.
+
+For example:  
+
+Given binary tree `[1,null,2,3]`,  
+```
+   1
+    \
+     2
+    /
+   3
+```
+
+return `[1,3,2]`.
+
+**Note:** Recursive solution is trivial, could you do it iteratively?
+
+## Solution
+- [Code](binarytreeinordertraversal.go)
+- [Testing](binarytreeinordertraversal_test.go)
+
+## Note
+- [中文](NOTE_Ch-zh.md)

solutions/binary_tree_inorder_traversal/README.md

@@ -0,0 +1,21 @@
+package binarytreeinordertraversal
+
+// TreeNode definition for a binary tree node.
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func inorderTraversal(root *TreeNode) []int {
+	var result []int
+	if root != nil {
+		// push all the left children from root node.
+		result = append(result, inorderTraversal(root.Left)...)
+		// push the root node
+		result = append(result, root.Val)
+		// push all the right children from root node.
+		result = append(result, inorderTraversal(root.Right)...)
+	}
+	return result
+}

solutions/binary_tree_inorder_traversal/binarytreeinordertraversal.go

@@ -0,0 +1,85 @@
+package binarytreeinordertraversal
+
+import (
+	"testing"
+
+	"github.com/WindomZ/testify/assert"
+)
+
+func Test_inorderTraversal(t *testing.T) {
+	assert.Empty(t, inorderTraversal(nil))
+	assert.Equal(t,
+		[]int{1},
+		inorderTraversal(&TreeNode{
+			Val: 1,
+		}))
+	assert.Equal(t,
+		[]int{1, 3, 2},
+		inorderTraversal(&TreeNode{
+			Val: 1,
+			Right: &TreeNode{
+				Val: 2,
+				Left: &TreeNode{
+					Val: 3,
+				},
+			},
+		}))
+	assert.Equal(t,
+		[]int{5, 3, 1, 2, 4, 6},
+		inorderTraversal(&TreeNode{
+			Val: 1,
+			Left: &TreeNode{
+				Val: 3,
+				Left: &TreeNode{
+					Val: 5,
+				},
+			},
+			Right: &TreeNode{
+				Val: 2,
+				Right: &TreeNode{
+					Val: 4,
+					Right: &TreeNode{
+						Val: 6,
+					},
+				},
+			},
+		}))
+}
+
+func Benchmark_inorderTraversal(b *testing.B) {
+	b.StopTimer()
+	b.ReportAllocs()
+	b.StartTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			inorderTraversal(nil)
+			inorderTraversal(&TreeNode{
+				Val: 1,
+				Right: &TreeNode{
+					Val: 2,
+					Left: &TreeNode{
+						Val: 3,
+					},
+				},
+			})
+			inorderTraversal(&TreeNode{
+				Val: 1,
+				Left: &TreeNode{
+					Val: 3,
+					Left: &TreeNode{
+						Val: 5,
+					},
+				},
+				Right: &TreeNode{
+					Val: 2,
+					Right: &TreeNode{
+						Val: 4,
+						Right: &TreeNode{
+							Val: 6,
+						},
+					},
+				},
+			})
+		}
+	})
+}