911. 在线选举

题目链接	911. 在线选举
思路	二分
题解链接	[Python/Java/JavaScript/Go] 二分查找
关键点	理解题意：预处理 - 按照times得出每个离散时刻下获胜者的person；询问 - 二分查找到>t的前一个时刻获胜者
时间复杂度	\(O(n)\)
空间复杂度	\(O(n)\)

代码实现：

class TopVotedCandidate:def __init__(self, persons: List[int], times: List[int]):n = len(times)self.times = timesself.answer = [-1] * ncnts = defaultdict(int)winner = Nonefor i, person in enumerate(persons):cnts[person] += 1if winner is None or cnts[person] >= cnts[winner]:winner = personself.answer[i] = winnerself.n = ndef q(self, t: int) -> int:left, right = -1, self.nwhile left + 1 < right:mid = (left+right) // 2if self.times[mid] <= t:left = midelse:right = midreturn self.answer[right - 1]

Python-标准库

class TopVotedCandidate:def __init__(self, persons: List[int], times: List[int]):n = len(times)self.times = timesself.answer = [-1] * ncnts = defaultdict(int)winner = Nonefor i, person in enumerate(persons):cnts[person] += 1if winner is None or cnts[person] >= cnts[winner]:winner = personself.answer[i] = winnerdef q(self, t: int) -> int:return self.answer[bisect_right(self.times, t) - 1]