結果

問題 No.1928 Make a Binary Tree
コンテスト
ユーザー gew1fw
提出日時 2025-06-12 20:13:59
言語 PyPy3
(7.3.15)
結果
WA  
実行時間 -
コード長 1,736 bytes
コンパイル時間 251 ms
コンパイル使用メモリ 82,060 KB
実行使用メモリ 174,264 KB
最終ジャッジ日時 2025-06-12 20:17:24
合計ジャッジ時間 23,793 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge5
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 * 3
other AC * 24 WA * 33
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():
    sys.setrecursionlimit(1 << 25)
    n = int(sys.stdin.readline())
    adj = [[] for _ in range(n+1)]
    for _ in range(n-1):
        x, y = map(int, sys.stdin.readline().split())
        adj[x].append(y)
        adj[y].append(x)
    
    # Build the tree with parent and children
    parent = [0] * (n + 1)
    children = [[] for _ in range(n + 1)]
    visited = [False] * (n + 1)
    q = deque([1])
    visited[1] = True
    while q:
        u = q.popleft()
        for v in adj[u]:
            if not visited[v] and v != parent[u]:
                parent[v] = u
                children[u].append(v)
                visited[v] = True
                q.append(v)
    
    # Iterative post-order traversal
    stack = [(1, False)]
    post_order = []
    while stack:
        node, processed = stack.pop()
        if processed:
            post_order.append(node)
        else:
            stack.append((node, True))
            # Push children in reverse order to process them in order
            for child in reversed(children[node]):
                stack.append((child, False))
    
    candidates = {}
    for node in post_order:
        merged = []
        for child in children[node]:
            merged.extend(candidates[child])
        merged.sort(reverse=True)
        sum_size = sum(merged[:2]) if len(merged) >= 2 else sum(merged)
        size = sum_size + 1
        new_candidates = [size]
        if len(merged) > 2:
            new_candidates.extend(merged[2:])
        # Truncate to at most two elements
        new_candidates = new_candidates[:2]
        candidates[node] = new_candidates
    
    print(candidates[1][0])

if __name__ == '__main__':
    main()
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