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website/content/ChapterFour/0145.Binary-Tree-Postorder-Traversal.md

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+# [145. Binary Tree Postorder Traversal](https://leetcode.com/problems/binary-tree-postorder-traversal/)
+
+## 题目
+
+
+Given a binary tree, return the postorder traversal of its nodes' values.
+
+
+
+**Example**:
+
+```
+
+Input: [1,null,2,3]
+   1
+    \
+     2
+    /
+   3
+
+Output: [3,2,1]
+
+```
+
+
+**Follow up**: Recursive solution is trivial, could you do it iteratively?
+
+
+ 
+
+## 题目大意
+
+后根遍历一颗树。
+
+## 解题思路
+
+递归的实现方法，见代码。
+
+
+
+
+
+## 代码
+
+```go
+
+package leetcode
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func postorderTraversal(root *TreeNode) []int {
+	var result []int
+	postorder(root, &result)
+	return result
+}
+
+func postorder(root *TreeNode, output *[]int) {
+	if root != nil {
+		postorder(root.Left, output)
+		postorder(root.Right, output)
+		*output = append(*output, root.Val)
+	}
+}
+
+```