結果

問題 No.1244 Black Segment
ユーザー lam6er
提出日時 2025-03-20 21:17:05
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 213 ms / 2,000 ms
コード長 1,233 bytes
コンパイル時間 176 ms
コンパイル使用メモリ 81,908 KB
実行使用メモリ 89,516 KB
最終ジャッジ日時 2025-03-20 21:17:58
合計ジャッジ時間 7,180 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge3
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 * 36
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 #
プレゼンテーションモードにする

import sys
from collections import deque
def main():
    n, m, A, B = map(int, sys.stdin.readline().split())
    target_start = B + 1
    if target_start > n + 1:
        print(-1)
        return
    graph = [[] for _ in range(n + 2)]  # Nodes from 1 to n+1
    for _ in range(m):
        L, R = map(int, sys.stdin.readline().split())
        a = L
        b = R + 1
        graph[a].append(b)
        graph[b].append(a)
    # Initialize distance array and queue
    distance = [-1] * (n + 2)
    q = deque()
    # Add all X in [1, A] as starting points
    for X in range(1, A + 1):
        if distance[X] == -1:
            distance[X] = 0
            q.append(X)
    # BFS to compute shortest paths
    while q:
        u = q.popleft()
        for v in graph[u]:
            if distance[v] == -1:
                distance[v] = distance[u] + 1
                q.append(v)
    # Find the minimum distance among nodes >= B+1
    min_dist = float('inf')
    for y_plus_1 in range(target_start, n + 2):
        if distance[y_plus_1] != -1:
            if distance[y_plus_1] < min_dist:
                min_dist = distance[y_plus_1]
    print(min_dist if min_dist != float('inf') else -1)
if __name__ == "__main__":
    main()
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