答案等于周长减去边界上相邻两个地点的最大距离。要求出每个地点离起点沿某个方向的距离，只需要快速定位每个点所在的边，我们分成水平和竖直两种情况，分别在对应的行或者列二分即可。
时间复杂度 $O((N+M)\log N)$。
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Discussion #1525 for Problem #17716. Campaign Speech
Type: Editorial
Status: Open
Posted by: jiangly
Posted at: 2026-04-15 16:03:37
Last updated: 2026-04-15 16:03:41
题解
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