输入：num = "1432219", k = 3
BitDefender (3 days)
Think about how you'd search a large room for a lost key. You wouldn't examine every square inch sequentially. You'd split the room into sections (by the couch, near the door, under the table) and rule out entire sections at a glance. "I didn't go near the kitchen, so skip that."，详情可参考91视频
Полина Кислицына (Редактор)
。旺商聊官方下载是该领域的重要参考
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