[模板] K-D tree

K-D tree有点像平衡树，但好像又不太像，就是一个来回切的分治建树，然后暴力加A*查询，详情见代码：

HDU - 2966

代码：

#include<iostream>
#include<cstdio>
#include<cmath>
#include<ctime>
#include<queue>
#include<algorithm>
#include<cstring>
using namespace std;
#define duke(i,a,n) for(register int i = a;i <= n;i++)
#define lv(i,a,n) for(register int i = a;i >= n;i--)
#define clean(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef double db;
const ll INF = 1e18;
template <class T>
void read(T &x)
{
    char c;
    bool op = 0;
    while(c = getchar(), c < '0' || c > '9')
        if(c == '-') op = 1;
    x = c - '0';
    while(c = getchar(), c >= '0' && c <= '9')
        x = x * 10 + c - '0';
    if(op) x = -x;
}
template <class T>
void write(T x)
{
    if(x < 0) putchar('-'), x = -x;
    if(x >= 10) write(x / 10);
    putchar('0' + x % 10);
}
const int N = 1e5 + 5;
int dim = 0,n = 0;
struct node
{
    int ch[2],id;
    ll d[2],minn[2],maxn[2];
    bool operator < (const node &oth) const
    {
        return d[dim] < oth.d[dim];
    }
}t[N << 2],a[N],b[N];
int root,tcnt = 0;
void push_up(int now)
{
    for(int i = 0;i < 2;i++)
    {
        if(t[now].ch[0])
        {
            t[now].minn[i] = min(t[now].minn[i],t[t[now].ch[0]].minn[i]);
            t[now].maxn[i] = max(t[now].maxn[i],t[t[now].ch[0]].maxn[i]);
        }
        if(t[now].ch[1])
        {
            t[now].minn[i] = min(t[now].minn[i],t[t[now].ch[1]].minn[i]);
            t[now].maxn[i] = max(t[now].maxn[i],t[t[now].ch[1]].maxn[i]);
        }
    }
}
void build(int &now,int d,int l,int r)
{
    if(l > r) return;
    dim = d;
    int mid = (l + r) >> 1;
    nth_element(a + l,a + mid,a + r + 1);
    t[now = ++ tcnt] = a[mid];t[now].id = a[mid].id;
    t[now].minn[0] = t[now].maxn[0] = t[now].d[0];
    t[now].maxn[1] = t[now].minn[1] = t[now].d[1];
    t[now].ch[0] = t[now].ch[1] = 0;
    build(t[now].ch[0],d ^ 1,l,mid - 1);
    build(t[now].ch[1],d ^ 1,mid + 1,r);
    push_up(now);
}
ll ans = INF;
ll dis(int now,ll *d)
{
    ll ret = 0;
    for(int i = 0;i < 2;i++)
    {
        ret += (t[now].d[i] - d[i]) * (t[now].d[i] - d[i]);
    }
    return ret;
}
ll price(int now,ll *d)
{
    ll ret = 0;
    for(int i = 0;i < 2;i++)
    {
        if(t[now].maxn[i] < d[i]) ret += (d[i] - t[now].maxn[i]) * (d[i] - t[now].maxn[i]);
        else if(t[now].minn[i] > d[i]) ret += (d[i] - t[now].minn[i]) * (d[i] - t[now].minn[i]);
    }
    return ret;
}
void query(int now,int id)
{
    if(!now) return;
    if(t[now].id ^ id) ans = min(ans,dis(now,b[id].d));
    ll disl = price(t[now].ch[0],b[id].d),disr = price(t[now].ch[1],b[id].d);
    if(disl < ans) query(t[now].ch[0],id);
    if(disr < ans) query(t[now].ch[1],id);
}
int T;
int main()
{
    read(T);
    while(T--)
    {
        tcnt = 0;
        read(n);
        duke(i,1,n)
        {
            read(a[i].d[0]);read(a[i].d[1]);
            a[i].id = i;
            b[i] = a[i];
        }
        build(root,0,1,n);
        duke(i,1,n)
        {
            ans = INF;
            query(root,i);
            printf("%lld
",ans);
        }
    }
    return 0; 
}