feat: add solutions to lc problem: No.0590

No.0590.N-ary Tree Postorder Traversal

Author: yanglbme

.prettierrc

@@ -2,7 +2,7 @@
     "tabWidth": 4,
     "useTabs": false,
     "semi": true,
-    "singleQuote": false,
+    "singleQuote": true,
     "TrailingCooma": "all",
     "bracketSpacing": true,
     "jsxBracketSameLine": false,

solution/0500-0599/0590.N-ary Tree Postorder Traversal/README.md

@@ -59,6 +59,8 @@
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
+递归：
+
 ```python
 """
 # Definition for a Node.
@@ -68,31 +70,284 @@ class Node:
         self.children = children
 """
 
+class Solution:
+    def postorder(self, root: 'Node') -> List[int]:
+        def dfs(root):
+            if root is None:
+                return
+            for child in root.children:
+                dfs(child)
+            ans.append(root.val)
+
+        ans = []
+        dfs(root)
+        return ans
+```
+
+迭代：
+
+```python
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val=None, children=None):
+        self.val = val
+        self.children = children
+"""
 
 class Solution:
     def postorder(self, root: 'Node') -> List[int]:
-        if not root:
+        if root is None:
             return []
-
-        def PO(root):
-            if root == None:
-                return res
-            else:
-                for i in root.children:
-                    PO(i)
-                    res.append(i.val)
-        res = []
-        PO(root)
-        res.append(root.val)
-        return res
+        stk = [root]
+        ans = []
+        while stk:
+            node = stk.pop()
+            ans.append(node.val)
+            if node.children:
+                for child in node.children:
+                    stk.append(child)
+        return ans[::-1]
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
+递归：
+
 ```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public List<Node> children;
+
+    public Node() {}
+
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, List<Node> _children) {
+        val = _val;
+        children = _children;
+    }
+};
+*/
+
+class Solution {
+
+    private List<Integer> ans;
+
+    public List<Integer> postorder(Node root) {
+        ans = new ArrayList<>();
+        dfs(root);
+        return ans;
+    }
+
+    private void dfs(Node root) {
+        if (root == null) {
+            return;
+        }
+        for (Node child : root.children) {
+            dfs(child);
+        }
+        ans.add(root.val);
+    }
+}
+
+```
+
+迭代：
+
+```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public List<Node> children;
+
+    public Node() {}
+
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, List<Node> _children) {
+        val = _val;
+        children = _children;
+    }
+};
+*/
+
+class Solution {
+
+    public List<Integer> postorder(Node root) {
+        if (root == null) {
+            return Collections.emptyList();
+        }
+        Deque<Node> stk = new ArrayDeque<>();
+        stk.offerLast(root);
+        LinkedList<Integer> ans = new LinkedList<>();
+        while (!stk.isEmpty()) {
+            Node node = stk.pollLast();
+            ans.addFirst(node.val);
+            if (node.children != null) {
+                for (Node child : node.children) {
+                    stk.offerLast(child);
+                }
+            }
+        }
+        return ans;
+    }
+}
+
+```
+
+### **C++**
+
+递归：
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    vector<Node*> children;
+
+    Node() {}
+
+    Node(int _val) {
+        val = _val;
+    }
+
+    Node(int _val, vector<Node*> _children) {
+        val = _val;
+        children = _children;
+    }
+};
+*/
+
+class Solution {
+public:
+    vector<int> postorder(Node* root) {
+        vector<int> ans;
+        dfs(root, ans);
+        return ans;
+    }
+
+    void dfs(Node* root, vector<int>& ans) {
+        if (!root) return;
+        for (auto& child : root->children) dfs(child, ans);
+        ans.push_back(root->val);
+    }
+};
+```
+
+迭代：
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    vector<Node*> children;
+
+    Node() {}
+
+    Node(int _val) {
+        val = _val;
+    }
+
+    Node(int _val, vector<Node*> _children) {
+        val = _val;
+        children = _children;
+    }
+};
+*/
+
+class Solution {
+public:
+    vector<int> postorder(Node* root) {
+        if (!root) return {};
+        stack<Node*> stk;
+        stk.push(root);
+        vector<int> ans;
+        while (!stk.empty())
+        {
+            auto& node = stk.top();
+            stk.pop();
+            ans.push_back(node->val);
+            for (auto& child : node->children)
+                stk.push(child);
+        }
+        reverse(ans.begin(), ans.end());
+        return ans;
+    }
+};
+```
+
+### **Go**
+
+递归：
+
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Children []*Node
+ * }
+ */
+
+func postorder(root *Node) []int {
+	var ans []int
+	var dfs func(root *Node)
+	dfs = func(root *Node) {
+		if root == nil {
+			return
+		}
+		for _, child := range root.Children {
+			dfs(child)
+		}
+		ans = append(ans, root.Val)
+	}
+	dfs(root)
+	return ans
+}
+```
 
+迭代：
+
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Children []*Node
+ * }
+ */
+
+func postorder(root *Node) []int {
+	if root == nil {
+		return []int{}
+	}
+	var stk []*Node
+	var ans []int
+	stk = append(stk, root)
+	for len(stk) > 0 {
+		node := stk[len(stk)-1]
+		stk = stk[:len(stk)-1]
+		ans = append([]int{node.Val}, ans...)
+		for _, child := range node.Children {
+			stk = append(stk, child)
+		}
+	}
+	return ans
+}
 ```
 
 ### **...**