Add Python n-ary postorder traversal goody (#504)

Closes #394.

Author: yulianka

.gitignore

@@ -10,3 +10,5 @@ yarn-error.log
 !.yarn/releases
 !.yarn/sdks
 !.yarn/versions
+
+.idea

workspaces/adventure-pack/goodies/python3/src/traverse_postorder_n_ary/__init__.py

@@ -0,0 +1,29 @@
+from typing import Generator, Optional, List
+
+
+class TreeNode:
+    def __init__(
+        self,
+        val: int = 0,
+        children: List["TreeNode"] = [],
+    ):
+        self.val = val
+        self.children = children
+
+
+def traverse_postorder_n_ary(
+    root: Optional[TreeNode],
+) -> Generator[TreeNode, None, None]:
+    stack = [(root, False)]
+    while stack:
+        node, did_traverse_children = stack.pop()
+        if not node:
+            continue
+
+        if did_traverse_children:
+            yield node
+            continue
+
+        stack.append((node, True))
+        for child in reversed(node.children):
+            stack.append((child, False))

workspaces/adventure-pack/goodies/python3/src/traverse_postorder_n_ary/goody.json

@@ -0,0 +1,3 @@
+{
+  "name": "traverse_postorder_n_ary"
+}

workspaces/adventure-pack/goodies/python3/src/traverse_postorder_n_ary/test.py

@@ -0,0 +1,58 @@
+from . import *
+
+
+def test_empty_tree() -> None:
+    assert list(traverse_postorder_n_ary(None)) == []
+
+
+def test_root_only() -> None:
+    root = TreeNode(10)
+    assert [node.val for node in traverse_postorder_n_ary(root)] == [10]
+
+
+def test_three_children() -> None:
+    root = TreeNode(10)
+    root.children = [TreeNode(4), TreeNode(5), TreeNode(6)]
+    assert [node.val for node in traverse_postorder_n_ary(root)] == [
+        4,
+        5,
+        6,
+        10,
+    ]
+
+
+def test_unbalanced_tree() -> None:
+    root = TreeNode(1)
+    root.children = [TreeNode(2)]
+    root.children[0].children = [TreeNode(3)]
+    root.children[0].children[0].children = [TreeNode(4)]
+
+    assert [node.val for node in traverse_postorder_n_ary(root)] == [4, 3, 2, 1]
+
+
+def test_large_tree() -> None:
+    root = TreeNode(1)
+    root.children = [TreeNode(2), TreeNode(3), TreeNode(4)]
+    root.children[0].children = [TreeNode(5), TreeNode(6)]
+    root.children[0].children[0].children = [TreeNode(8), TreeNode(9)]
+    root.children[0].children[0].children[1].children = [
+        TreeNode(11),
+        TreeNode(12),
+    ]
+    root.children[0].children[1].children = [TreeNode(10)]
+    root.children[2].children = [TreeNode(7)]
+
+    assert [node.val for node in traverse_postorder_n_ary(root)] == [
+        8,
+        11,
+        12,
+        9,
+        5,
+        10,
+        6,
+        2,
+        3,
+        7,
+        4,
+        1,
+    ]

workspaces/adventure-pack/src/app/__tests__/__snapshots__/equip-test.ts.snap

@@ -3042,6 +3042,44 @@ def traverse_postorder(
 ########################### END ADVENTURE PACK CODE ############################"
 `;
 
+exports[`App can equip single goody: Python 3 traverse_postorder_n_ary 1`] = `
+"########################## BEGIN ADVENTURE PACK CODE ###########################
+# Adventure Pack commit fake-commit-hash
+# Running at: https://example.com/
+
+from typing import Generator, Optional, List
+
+
+class TreeNode:
+    def __init__(
+        self,
+        val: int = 0,
+        children: List["TreeNode"] = [],
+    ):
+        self.val = val
+        self.children = children
+
+
+def traverse_postorder_n_ary(
+    root: Optional[TreeNode],
+) -> Generator[TreeNode, None, None]:
+    stack = [(root, False)]
+    while stack:
+        node, did_traverse_children = stack.pop()
+        if not node:
+            continue
+
+        if did_traverse_children:
+            yield node
+            continue
+
+        stack.append((node, True))
+        for child in reversed(node.children):
+            stack.append((child, False))
+
+########################### END ADVENTURE PACK CODE ############################"
+`;
+
 exports[`App can equip single goody: Python 3 traverse_preorder 1`] = `
 "########################## BEGIN ADVENTURE PACK CODE ###########################
 # Adventure Pack commit fake-commit-hash

workspaces/adventure-pack/src/app/__tests__/__snapshots__/render-test.ts.snap

@@ -1748,6 +1748,38 @@ def traverse_postorder(
         stack.append((node.left, False))"
 `;
 
+exports[`App can render goody: Python 3 traverse_postorder_n_ary 1`] = `
+"from typing import Generator, Optional, List
+
+
+class TreeNode:
+    def __init__(
+        self,
+        val: int = 0,
+        children: List["TreeNode"] = [],
+    ):
+        self.val = val
+        self.children = children
+
+
+def traverse_postorder_n_ary(
+    root: Optional[TreeNode],
+) -> Generator[TreeNode, None, None]:
+    stack = [(root, False)]
+    while stack:
+        node, did_traverse_children = stack.pop()
+        if not node:
+            continue
+
+        if did_traverse_children:
+            yield node
+            continue
+
+        stack.append((node, True))
+        for child in reversed(node.children):
+            stack.append((child, False))"
+`;
+
 exports[`App can render goody: Python 3 traverse_preorder 1`] = `
 "from typing import Generator, Optional