結果
問題 |
No.1976 Cut then Connect
|
ユーザー |
![]() |
提出日時 | 2025-03-05 14:23:40 |
言語 | PyPy3 (7.3.15) |
結果 |
AC
|
実行時間 | 346 ms / 2,000 ms |
コード長 | 2,229 bytes |
コンパイル時間 | 636 ms |
コンパイル使用メモリ | 82,600 KB |
実行使用メモリ | 104,068 KB |
最終ジャッジ日時 | 2025-03-05 14:23:49 |
合計ジャッジ時間 | 8,424 ms |
ジャッジサーバーID (参考情報) |
judge3 / judge2 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 2 |
other | AC * 31 |
ソースコード
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 def rerooting(root=0): uu = [] stack = [root] while stack: u = stack.pop() uu.append(u) vv = [] # !!!check the format of the "to"!!! for v in to[u]: if v == par[u]: continue vv.append(v) par[v] = u stack.append(v) rdp[v] = dp[u] to[u] = vv # bottom up for u in uu[::-1]: p = par[u] if p != -1: trans_up(u) dp[p] = op(dp[p], dp[u]) # top down for u in uu: cs = e() # !!!check the format of the "to"!!! for v in to[u]: rdp[v] = op(rdp[v], cs) cs = op(cs, dp[v]) cs = rdp[u] for v in to[u][::-1]: rdp[v] = op(rdp[v], cs) trans_down(v) cs = op(cs, dp[v]) # dp[u] = cs def op(a, b): return (max(a[0],b[0]),max(a[1],b[1],a[0]+b[0])) # u to parent[u] def trans_up(u): dp[u] = (dp[u][0]+1,dp[u][1]) return # parent[u] to u def trans_down(u): rdp[u] = (rdp[u][0]+1,rdp[u][1]) return n=II() to=[[] for _ in range(n)] for _ in range(n-1): u,v=LI1() to[u].append(v) to[v].append(u) e = lambda: (0,0) par = [-1]*n # dp初期化 dp = [e() for _ in range(n)] rdp = [e() for _ in range(n)] rerooting() ans=n for u in range(1,n): cur=max(dp[u][1],rdp[u][1],(dp[u][1]+1)//2+(rdp[u][1]+1)//2+1) ans=min(ans,cur) # print(dp) # print(rdp) print(ans)