from typing import Callable, Generic, List, TypeVar T = TypeVar("T") class Rerooting(Generic[T]): __slots__ = ("adjList", "_n", "_decrement") def __init__(self, n: int, decrement: int = 0): self.adjList = [[] for _ in range(n)] self._n = n self._decrement = decrement def addEdge(self, u: int, v: int) -> None: u -= self._decrement v -= self._decrement self.adjList[u].append(v) self.adjList[v].append(u) def rerooting( self, e: Callable[[int], T], op: Callable[[T, T], T], composition: Callable[[T, int, int, int], T], root=0, ) -> List["T"]: root -= self._decrement assert 0 <= root < self._n parents = [-1] * self._n order = [root] stack = [root] while stack: cur = stack.pop() for next in self.adjList[cur]: if next == parents[cur]: continue parents[next] = cur order.append(next) stack.append(next) dp1 = [e(i) for i in range(self._n)] dp2 = [e(i) for i in range(self._n)] for cur in order[::-1]: res = e(cur) for next in self.adjList[cur]: if parents[cur] == next: continue dp2[next] = res res = op(res, composition(dp1[next], cur, next, 0)) res = e(cur) for next in self.adjList[cur][::-1]: if parents[cur] == next: continue dp2[next] = op(res, dp2[next]) res = op(res, composition(dp1[next], cur, next, 0)) dp1[cur] = res for newRoot in order[1:]: parent = parents[newRoot] dp2[newRoot] = composition(op(dp2[newRoot], dp2[parent]), parent, newRoot, 1) dp1[newRoot] = op(dp1[newRoot], dp2[newRoot]) return dp1