結果

問題 No.274 The Wall
コンテスト
ユーザー 前田悠真
提出日時 2025-06-09 18:04:33
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 215 ms / 2,000 ms
コード長 3,414 bytes
コンパイル時間 567 ms
コンパイル使用メモリ 83,036 KB
実行使用メモリ 80,512 KB
最終ジャッジ日時 2025-06-09 18:04:38
合計ジャッジ時間 5,292 ms
ジャッジサーバーID
（参考情報） 		judge3 / judge4
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 * 4
other AC * 23
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 typing
import sys

class CSR:
    def __init__(
            self, n: int, edges: typing.List[typing.Tuple[int, int]]) -> None:
        self.start = [0] * (n + 1)
        self.elist = [0] * len(edges)

        for e in edges:
            self.start[e[0] + 1] += 1

        for i in range(1, n + 1):
            self.start[i] += self.start[i - 1]

        counter = self.start.copy()
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class SCCGraph:
    '''
    Reference:
    R. Tarjan,
    Depth-First Search and Linear Graph Algorithms
    '''

    def __init__(self, n: int) -> None:
        self._n = n
        self._edges: typing.List[typing.Tuple[int, int]] = []

    def num_vertices(self) -> int:
        return self._n

    def add_edge(self, from_vertex: int, to_vertex: int) -> None:
        self._edges.append((from_vertex, to_vertex))
    
    def scc_ids(self) -> typing.Tuple[int, typing.List[int]]:
        g = CSR(self._n, self._edges)
        now_ord = 0
        group_num = 0
        visited = []
        low = [0] * self._n
        order = [-1] * self._n
        ids = [0] * self._n

        sys.setrecursionlimit(max(self._n + 1000, sys.getrecursionlimit()))

        def dfs(v: int) -> None:
            nonlocal now_ord
            nonlocal group_num
            nonlocal visited
            nonlocal low
            nonlocal order
            nonlocal ids

            low[v] = now_ord
            order[v] = now_ord
            now_ord += 1
            visited.append(v)
            for i in range(g.start[v], g.start[v + 1]):
                to = g.elist[i]
                if order[to] == -1:
                    dfs(to)
                    low[v] = min(low[v], low[to])
                else:
                    low[v] = min(low[v], order[to])

            if low[v] == order[v]:
                while True:
                    u = visited[-1]
                    visited.pop()
                    order[u] = self._n
                    ids[u] = group_num
                    if u == v:
                        break
                group_num += 1

        for i in range(self._n):
            if order[i] == -1:
                dfs(i)

        for i in range(self._n):
            ids[i] = group_num - 1 - ids[i]

        return group_num, ids

    def scc(self) -> typing.List[typing.List[int]]:
        ids = self.scc_ids()
        group_num = ids[0]
        counts = [0] * group_num
        for x in ids[1]:
            counts[x] += 1
        groups: typing.List[typing.List[int]] = [[] for _ in range(group_num)]
        for i in range(self._n):
            groups[ids[1][i]].append(i)

        return groups

n, m = map(int, input().split())

LR = [tuple(map(int, input().split())) for _ in range(n)]

# from atcoder.twosat import TwoSAT

ts = SCCGraph(2*n)

def add(n1, f, n2, g):
   ts.add_edge(2*n1+1*(not f), 2*n2+1*g)
   ts.add_edge(2*n2+1*(not g), 2*n1+1*f)

for i in range(n):
  l, r = LR[i]
  l_, r_ = m-1-r, m-1-l
  for j in range(i+1, n):
    ll, rr = LR[j]
    if not (r<ll or rr<l) and not (r_<ll or rr<l_):
      print('NO')
      exit()
    if not (r<ll or rr<l):
      add(i, 0, j, 0)
      add(i, 1, j, 1)
    elif not (r_<ll or rr<l_):
      add(i, 0, j, 1)
      add(i, 1, j, 0)
  
_, G = ts.scc_ids()

# print(G)
for i in range(n):
  if G[2*i]==G[2*i+1]:
      print('NO')
      exit()
  
print('YES')
0