結果

問題 No.1094 木登り / Climbing tree
ユーザー lam6er
提出日時 2025-03-20 21:11:43
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 991 ms / 2,000 ms
コード長 2,177 bytes
コンパイル時間 371 ms
コンパイル使用メモリ 82,928 KB
実行使用メモリ 211,948 KB
最終ジャッジ日時 2025-03-20 21:13:00
合計ジャッジ時間 23,307 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge1
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ファイルパターン 結果
sample AC * 1
other AC * 26
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
from collections import deque

def main():
    data = sys.stdin.read().split()
    idx = 0

    N = int(data[idx])
    idx += 1

    edges = [[] for _ in range(N + 1)]  # 1-based indexing

    for _ in range(N - 1):
        a = int(data[idx])
        b = int(data[idx + 1])
        c = int(data[idx + 2])
        edges[a].append((b, c))
        edges[b].append((a, c))
        idx += 3

    # BFS to set parent, depth, and distance from root
    parent = [0] * (N + 1)
    depth = [0] * (N + 1)
    dist = [0] * (N + 1)
    root = 1

    q = deque([root])
    parent[root] = 0
    depth[root] = 0
    dist[root] = 0

    while q:
        u = q.popleft()
        for v, c in edges[u]:
            if parent[u] != v and parent[v] == 0:
                parent[v] = u
                depth[v] = depth[u] + 1
                dist[v] = dist[u] + c
                q.append(v)

    # Precompute binary lifting table for LCA
    log_max = 20
    table = [[0] * (N + 1) for _ in range(log_max)]
    table[0] = parent[:]  # Base case: direct parent

    for k in range(1, log_max):
        for v in range(1, N + 1):
            table[k][v] = table[k - 1][table[k - 1][v]]

    # Function to find LCA using binary lifting
    def get_lca(u, v):
        if depth[u] < depth[v]:
            u, v = v, u

        # Bring u to the depth of v
        for k in range(log_max - 1, -1, -1):
            if depth[u] - (1 << k) >= depth[v]:
                u = table[k][u]

        if u == v:
            return u

        # Now bring both up until LCA is found
        for k in range(log_max - 1, -1, -1):
            if table[k][u] != table[k][v]:
                u = table[k][u]
                v = table[k][v]

        return table[0][u]

    # Process queries
    Q = int(data[idx])
    idx += 1
    results = []
    for _ in range(Q):
        s = int(data[idx])
        t = int(data[idx + 1])
        idx += 2

        if s == t:
            results.append(0)
            continue

        lca_node = get_lca(s, t)
        result = dist[s] + dist[t] - 2 * dist[lca_node]
        results.append(result)

    print('\n'.join(map(str, results)))

if __name__ == '__main__':
    main()
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