BZOJ 2177 最小曼哈顿生成树

留板。

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> pii;
const int maxn=100005;
const long long inf=0x3f3f3f3f3f3f3f3f;
int n,pos[maxn],f[maxn];
long long bit[maxn],res,x,y;
struct edge {
int u,v;
long long w;
edge(){}
edge(int u,int v,int w):u(u),v(v),w(w){}
bool operator<(const edge &rhs)const{
return w<rhs.w;
}
};
vector<edge> v;
vector<long long> ID;
inline void init() {
for (int i=0;i<n;++i)
f[i]=i;
}
int F(int x) {
return x==f[x]?x:f[x]=F(f[x]);
}
inline void U(int x,int y) {
f[F(x)]=F(y);
}
inline void update(int x,long long v,int p) {
while (x) {
if (bit[x]>v) {
bit[x]=v;
pos[x]=p;
}
x-=x&-x;
}
}
inline int query(int x) {
long long val=inf;
int ret=-1;
while (x<=n) {
if (bit[x]<val) {
val=bit[x];
ret=pos[x];
}
x+=x&-x;
}
return ret;
}
struct P {
long long x,y;
int id;
P(){}
P(long long x,long long y,int id):x(x),y(y),id(id){}
bool operator<(const P &rhs)const{
return x==rhs.x?y<rhs.y:x<rhs.x;
}
} p[maxn];
inline long long manh(int i,int j) {
return abs(p[i].x-p[j].x)+abs(p[i].y-p[j].y);
}
inline void discrete() {
ID.clear();
for (int i=0;i<n;++i)
ID.push_back(p[i].y-p[i].x);
sort(ID.begin(),ID.end());
ID.erase(unique(ID.begin(),ID.end()),ID.end());
}
inline int id(int x) {
return lower_bound(ID.begin(),ID.end(),x)-ID.begin()+1;
}
inline void solve() {
sort(p,p+n);
discrete();
memset(bit,0x3f,sizeof bit);
memset(pos,-1,sizeof pos);
for (int i=n-1;i>=0;--i) {
int o=id(p[i].y-p[i].x);
int t=query(o);
if (t!=-1)
v.push_back(edge(p[i].id,p[t].id,manh(i,t)));
update(o,p[i].x+p[i].y,i);
}
}
inline void build() {
for (int i=0;i<4;++i) {
if (i==1||i==3)
for (int j=0;j<n;++j)
swap(p[j].x,p[j].y);
if (i==2)
for (int j=0;j<n;++j)
p[j].x=-p[j].x;
solve();
}
}
inline void kruskal() {
init();
sort(v.begin(),v.end());
res=0;
for (int i=0;i<(int)v.size();++i)
if (F(v[i].u)!=F(v[i].v)) {
U(v[i].u,v[i].v);
res+=v[i].w;
}
cout<<res<<endl;
}
int main()
{
scanf("%d",&n);
for (int i=0;i<n;++i) {
cin>>x>>y;
p[i]=P(x,y,i);
}
build();
kruskal();
return 0;
}