py sol for Game on Tree

solutions/advanced/ac-GameOnTree.mdx

@@ -7,6 +7,8 @@ author: Aakash Gokhale
 
 [Official Editorial (Japanese)](https://atcoder.jp/contests/agc017/editorial)
 
+## Explanation
+
 Since the game in the problem seems similar to Nim, let's try to use Sprague-Grundy numbers.
 
 To solve the problem, for a certain root with subtrees, $s_1, s_2, ..., s_k$, we can try to convert all these subtrees into a stack of some size.
@@ -39,6 +41,7 @@ This makes sense because whichever edge that Alice chooses, Bob can choose the o
 #include <functional>
 #include <iostream>
 #include <vector>
+
 using namespace std;
 
 int main() {
@@ -71,4 +74,45 @@ int main() {
 ```
 
 </CPPSection>
+<PySection>
+
+<Warning>
+
+The below solution only works when you submit with PyPy.
+Submitting with normal Python will result in MLE.
+
+</Warning>
+
+```py
+import sys, pypyjit
+
+# improves performance for deeply recursive functions by allowing PyPy to skip unrolling
+pypyjit.set_param("max_unroll_recursion=-1")
+
+sys.setrecursionlimit(10**7)
+
+
+def dfs(u: int, p: int) -> int:
+	sg = 0
+	for v in g[u]:
+		if v != p:
+			# Adding 1 because the edge from u to v increases the size of
+			# each stack by 1
+			sg ^= dfs(v, u) + 1
+
+	return sg
+
+
+n = int(input())
+g = [[] for _ in range(n + 1)]
+
+for _ in range(n - 1):
+	u, v = map(int, input().split())
+	g[u].append(v)
+	g[v].append(u)
+
+print("Alice" if dfs(1, 0) else "Bob")
+```
+
+</PySection>
 </LanguageSection>