Submission #7491385

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Source Code Expand

import sys
sys.setrecursionlimit(10**8)
def resolve():
    import math
    class DoublingLCA:
        """
        construct: O(NlogN)
        query O(logN)
        """

        def __init__(self,edges,root=0):
            """
            :param list of (list of int) edges:
            :param int root=0:
            """
            self.edges = edges
            self.n = len(edges)
            self.logn = (self.n-1).bit_length()
            self.depths = [-1] * self.n
            self.parents = [[-1] * self.n for _ in range(self.logn)]
            # construct
            self.__dfs(-1,root,0)
            self.__doubling()

        def __dfs(self,par,cur,dep):
            self.depths[cur]=dep
            self.parents[0][cur]=par
            for v in self.edges[cur]:
                if v!=par:
                    self.__dfs(cur,v,dep+1)

        def __doubling(self):
            for i in range(1,self.logn):
                for v in range(self.n):
                    if self.parents[i-1][v] < 0: # 親が存在しないとき。-1を通すとlistの末尾を取得してしまう
                        continue
                    self.parents[i][v]=self.parents[i-1][self.parents[i-1][v]]

        def get(self, u, v):
            # 深さを合わせる
            dd=self.depths[v]-self.depths[u]
            if dd<0:
                u, v = v, u
                dd*=-1
            for i in range(self.logn):
                if dd&(1<<i):
                    v = self.parents[i][v]

            if v==u: return v # 高さ揃えた時点で一致してたら終わり

            # にぶたん
            for i in reversed(range(self.logn)):
                pu,pv=self.parents[i][u],self.parents[i][v]
                if pu!=pv:
                    u,v=pu,pv
            return self.parents[0][u]

    # input
    N = int(input())
    XY = [list(map(int, input().split())) for _ in range(N-1)]
    Q = int(input())
    AB = [list(map(int, input().split())) for _ in range(Q)]

    edges = [[] for _ in range(N)]
    for x, y in XY:
        edges[x-1].append(y-1)
        edges[y-1].append(x-1)
    lca = DoublingLCA(edges)

    for u,v in AB:
        u=u-1
        v=v-1
        print(lca.depths[u]+lca.depths[v]-2*lca.depths[lca.get(u,v)]+1)

resolve()

Submission Info

Judge Result