poj3241

曼哈顿最小树。

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<bitset>
#include<map>
//#include<regex>
#include<cstdio>
#pragma GCC optimize(2)
#define up(i,a,b)  for(int i=a;i<b;i++)
#define dw(i,a,b)  for(int i=a;i>b;i--)
#define upd(i,a,b) for(int i=a;i<=b;i++)
#define dwd(i,a,b) for(int i=a;i>=b;i--)
//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
	char ch = getchar(); ll x = 0, f = 1;
	while (ch<'0' || ch>'9') { if (ch == '-')f = -1; ch = getchar(); }
	while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); }
	return x * f;
}
typedef pair<int, int> pir;
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
#define lrt root<<1
#define rrt root<<1|1
const int N = 10010;
struct eg {
	int u, v, wi;
	bool operator<(const eg a) {
		return wi < a.wi;
	}
}edge[5 * N];
int eg_cnt = 0;
void addedge(int u, int v, int wi)
{
	edge[eg_cnt].u = u; edge[eg_cnt].v = v; edge[eg_cnt].wi = wi; eg_cnt++;
}
struct uni {
	int height[N], fa[N];
	void init(int maxn)
	{
		upd(i, 0, maxn)
		{
			height[i] = 1;
			fa[i] = i;
		}
	}
	int find_pr(int x)
	{
		return x == fa[x] ? x : fa[x] = find_pr(fa[x]);
	}
	void unit(int x, int y)
	{
		x = find_pr(x);
		y = find_pr(y);
		if (x == y)return;
		if (height[x] < height[y])swap(x, y);
		fa[y] = x;
		height[x] += height[y];
	}
	bool same(int x, int y)
	{
		return find_pr(x) == find_pr(y);
	}
}un;
struct dij{
	int a, b, id;
	bool operator<(const dij tp)const
	{
		return a == tp.a ? b < tp.b : a < tp.a;
	}
}now[N];
struct bit {
	int minn[N];
	int id[N];
	int len;
	void init(int len)
	{
		this->len = len;
		memset(bit::minn, INF, sizeof(bit::minn));
		memset(bit::id, 0, sizeof(bit::id));
	}
	int lowbit(int i)
	{
		return i & (-i);
	}
	void update(int pos, int val,int id)
	{
		while (pos)
		{
			if (minn[pos] > val)
			{
				bit::minn[pos] = val;
				bit::id[pos] = id;
			}
			pos -= bit::lowbit(pos);
		}
	}
	int query(int pos)
	{
		int temp_min = INF;
		int temp_pos = 0;
		while (pos <= len)
		{
			if (temp_min > minn[pos])
			{
				temp_min = minn[pos];
				temp_pos = id[pos];
			}
			pos += bit::lowbit(pos);
		}
		return temp_pos;
	}
}BIT;
int n, k;
vector<int>vec;
int distemp[N];
int dist(int x, int y)
{
	return abs(now[x].b - now[y].b) + abs(now[x].a - now[y].a);
}
void cal()
{
	upd(i, 1, n)
	{
		distemp[i] = now[i].b - now[i].a;
		vec.push_back(distemp[i]);
	}
	sort(vec.begin(), vec.end());
	vec.erase(unique(vec.begin(), vec.end()), vec.end());
	BIT.init(vec.size());
	dwd(i, n, 1)
	{
		int cal_pos = lower_bound(vec.begin(), vec.end(), distemp[i]) - vec.begin() + 1;
		int f_pos = BIT.query(cal_pos);
		if (f_pos != 0)
			addedge(now[i].id, now[f_pos].id, dist(i, f_pos));
		BIT.update(cal_pos, now[i].a + now[i].b, i);
	}
}
void kruskal()
{
	k = n - k;
	int kru_tot = 0;
	sort(edge, edge + eg_cnt);
	vector<int>ans;
	up(i, 0, eg_cnt)
	{
		if (!un.same(edge[i].u, edge[i].v))
		{
			kru_tot++;
			un.unit(edge[i].u, edge[i].v);
			if (kru_tot == k) { printf("%d\n", edge[i].wi); return; }
			//ans.push_back(edge[i].wi);
		}
	}
	//for (auto p : ans)printf("%d ", p);
	//printf("%d\n", ans[n - k]);
}
int main()
{
	n = read(), k = read();
	un.init(n);
	upd(i, 1, n)
	{
		now[i].a = read(); now[i].b = read(); now[i].id = i;
	}
	up(j, 0, 4)
	{
		if (j == 1||j==3)
		{
			upd(i, 1, n)swap(now[i].a, now[i].b);
		}
		else if (j == 2)
		{
			upd(i, 1, n)now[i].a = -now[i].a;
		}
		sort(now + 1, now + n + 1);
		cal();
	}
	kruskal();
	return 0;
}