結果

問題 No.274 The Wall
ユーザー N-noa21
提出日時 2024-06-08 01:11:13
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 211 ms / 2,000 ms
コード長 2,078 bytes
コンパイル時間 450 ms
コンパイル使用メモリ 82,432 KB
実行使用メモリ 79,232 KB
最終ジャッジ日時 2024-12-26 14:19:07
合計ジャッジ時間 4,995 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge5
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ファイルパターン 結果
sample AC * 4
other AC * 22
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ソースコード

diff #
プレゼンテーションモードにする

#https://tjkendev.github.io/procon-library/python/graph/2-sat.html
from collections import deque
def scc(N, G, RG):
    order = []
    used = [0]*N
    def dfs(s):
        used[s] = 1
        for t in G[s]:
            if not used[t]:
                dfs(t)
        order.append(s)
    for i in range(N):
        if not used[i]:
            dfs(i)
    group = [-1]*N
    label = 0
    order.reverse()
    for s in order:
        if group[s] != -1:
            continue
        que = deque([s])
        group[s] = label
        while que:
            v = que.popleft()
            for w in RG[v]:
                if group[w] != -1:
                    continue
                que.append(w)
                group[w] = label
        label += 1
    return group # topological ordering
N,M = map(int, input().split())
G = [[] for i in range(2*M)]
RG = [[] for i in range(2*M)]
# add (a ∨ b)
# a =  x_i if neg_i = 0
# a = ~x_i if neg_i = 1
def add_edge(i, neg_i, j, neg_j):#
    #print(i,neg_i,j,neg_j)
    if neg_i:
        i0 = i+M; i1 = i
    else:
        i0 = i; i1 = i+M
    if neg_j:
        j0 = j+M; j1 = j
    else:
        j0 = j; j1 = j+M
    # add (~a ⇒ b)
    G[i1].append(j0); RG[j0].append(i1)
    # add (~b ⇒ a)
    G[j1].append(i0); RG[i0].append(j1)
# check if the formula is satisfiable
def check(group):
    for i in range(M):
        if group[i] == group[i+M]:
            return False
    return True
l = [tuple(map(int, input().split())) for i in range(N)]
for i in range(N):
    L1,R1 = l[i]
    r_R1,r_L1 = M-L1-1,M-R1-1
    for j in range(i+1,N):
        L2,R2 = l[j]
        flag1,flag2 = False,False
        r_R2,r_L2 = M-L2-1,M-R2-1
        if (L1 <= R2 and L2 <= R1):
            flag1 = True
            add_edge(i, 0, j, 0)
            add_edge(i, 1, j, 1)
        if (L1 <= r_R2 and r_L2 <= R1):
            flag2 = True
            add_edge(i, 0, j, 1)
            add_edge(i, 1, j, 0)
        if flag1 and flag2:
            print("NO")
            exit()
group = scc(2*M, G, RG)
if check(group):
    print("YES")
else:
    print("NO")
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