[BZOJ1604] [Usaco2008 Open]Cow Neighborhoods 奶牛的邻居（好题）传送门
良心题解
#include <set>
#include <cstdio>
#include <iostream>
#include <algorithm>
#define N 100001
#define LL long long
#define INF (~(1 << 31))
us
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