104 accepted. 12ms > 9ms.

Author: aQua

Algorithms/0104.maximum-depth-of-binary-tree/README.md

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+# [104. Maximum Depth of Binary Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/)
+
+## 题目
+Given a binary tree, find its maximum depth.
+
+The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
+
+## 解题思路
+
+见程序注释

Algorithms/0104.maximum-depth-of-binary-tree/maximum-depth-of-binary-tree.go

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+package Problem0104
+
+import (
+	"github.com/aQuaYi/LeetCode-in-Golang/kit"
+)
+
+type TreeNode = kit.TreeNode
+
+func maxDepth(root *TreeNode) int {
+	res := 0 
+
+	var dfs func(*TreeNode, int)
+	dfs = func(root *TreeNode, level int) {
+		if root == nil {
+			return
+		}
+
+		// 出现了新的 level
+		if res < level {
+			res = level
+		}
+
+		dfs(root.Left, level+1)
+		dfs(root.Right, level+1)
+	}
+
+	dfs(root, 1)
+
+	return res
+}

Algorithms/0104.maximum-depth-of-binary-tree/maximum-depth-of-binary-tree_test.go

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+package Problem0104
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/aQuaYi/LeetCode-in-Golang/kit"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Problem0104(t *testing.T) {
+	ast := assert.New(t)
+
+	// tcs is testcase slice
+	tcs := []struct {
+		pre, in []int
+		ans     int
+	}{
+
+		{
+			[]int{},
+			[]int{},
+			0,
+		},
+
+		{
+			[]int{3, 9, 20, 15, 7},
+			[]int{9, 3, 15, 20, 7},
+			3,
+		},
+
+		// 可以多个 testcase
+	}
+
+	for _, tc := range tcs {
+		fmt.Printf("~~%v~~\n", tc)
+
+		ast.Equal(tc.ans, maxDepth(kit.PreIn2Tree(tc.pre, tc.in)), "输入:%v", tc)
+	}
+}