結果

問題 No.2337 Equidistant
コンテスト
ユーザー mkawa2
提出日時 2024-09-10 21:33:49
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 1,283 ms / 4,000 ms
コード長 2,633 bytes
コンパイル時間 486 ms
コンパイル使用メモリ 82,556 KB
実行使用メモリ 146,992 KB
最終ジャッジ日時 2024-09-10 21:34:10
合計ジャッジ時間 21,503 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 1
other AC * 28
権限があれば一括ダウンロードができます

ソースコード

diff # 

import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

class LCA:
    def __init__(self, parent, depth):
        n = len(parent)
        self._depth = depth
        log = max(self._depth).bit_length()
        self._table = [parent]+[[-1]*n for _ in range(log)]
        row0 = self._table[0]
        for lv in range(log):
            row1 = self._table[lv+1]
            for u in range(n):
                if row0[u] == -1: continue
                row1[u] = row0[row0[u]]
            row0 = row1

    def anc(self, u, v):
        diff = self._depth[u]-self._depth[v]
        if diff < 0: u, v = v, u
        diff = abs(diff)
        u = self.up(u, diff)
        if u == v: return u,-1,-1
        for lv in range(self._depth[u].bit_length()-1, -1, -1):
            anclv = self._table[lv]
            if anclv[u] != anclv[v]: u, v = anclv[u], anclv[v]
        return self._table[0][u],u,v

    def up(self, u, dist):
        lv = 0
        while dist and u != -1:
            if dist & 1: u = self._table[lv][u]
            lv, dist = lv+1, dist >> 1
        return u

n,q=LI()
to=[[] for _ in range(n)]
for _ in range(n-1):
    u,v=LI1()
    to[u].append(v)
    to[v].append(u)

def dfs(root=0):
    uu, stack = [], [root]
    while stack:
        u = stack.pop()
        uu.append(u)
        for v in to[u]:
            if v == parent[u]: continue
            parent[v] = u
            depth[v] = depth[u]+1
            stack.append(v)
    return uu

parent, depth = [-1]*n, [0]*n
uu = dfs()
dp=[1]*n
for u in uu[:0:-1]:
    p=parent[u]
    dp[p]+=dp[u]

lca=LCA(parent,depth)
for _ in range(q):
    u,v=LI1()
    a,pu,pv=lca.anc(u,v)
    d=depth[u]+depth[v]-depth[a]*2
    if d&1:
        print(0)
    elif depth[u]==depth[v]:
        print(n-dp[pu]-dp[pv])
    else:
        if depth[u]>depth[v]:
            u,v=v,u
            pu,pv=pv,pu
        pv=lca.up(v,d//2-1)
        m=parent[pv]
        print(dp[m]-dp[pv])
0