hdu4347The Closest M Points kdtree

kdtree讲解：

https://blog.csdn.net/qing101hua/article/details/53228668

https://blog.csdn.net/acdreamers/article/details/44664645

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4347

给你一堆点，每次查询给一个点求和这个点最近的m个点是什么（距离是欧氏距离）

裸的kdtree

//#pragma comment(linker, "/stack:200000000")
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pi acos(-1.0)
#define ll long long
#define vi vector<int>
#define mod 1000000007
#define C 0.5772156649
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#define pil pair<int,ll>
#define pli pair<ll,int>
#define pii pair<int,int>
#define cd complex<double>
#define ull unsigned long long
#define base 1000000000000000000
#define fio ios::sync_with_stdio(false);cin.tie(0)

using namespace std;

const double g=10.0,eps=1e-8;
const int N=50000+10,maxn=5000+10,inf=0x3f3f3f3f,INF=0x3f3f3f3f3f3f3f3f;

int n,k,idx;
struct node{
    int f[5];
    bool operator <(const node&rhs)const{
        return f[idx]<rhs.f[idx];
    }
}a[N];
priority_queue<pair<double,node> >q;
struct kdtree{
    bool vis[N<<2];
    node date[N<<2];
    void build(int l,int r,int rt,int dep)
    {
        if(l>r)return ;
        vis[rt]=1;
        vis[rt<<1]=vis[rt<<1|1]=0;
        idx=dep%k;
        int m=(l+r)>>1;
        nth_element(a+l,a+m,a+r+1);
        date[rt]=a[m];
        build(l,m-1,rt<<1,dep+1);
        build(m+1,r,rt<<1|1,dep+1);
    }
    void query(node p,int m,int rt,int dep)
    {
        if(!vis[rt])return ;
        printf("%d \n",rt);
        pair<double,node>cur(0,date[rt]);
        for(int i=0;i<k;i++)
            cur.fi+=(cur.se.f[i]-p.f[i])*(cur.se.f[i]-p.f[i]);
        int dim=dep%k;
        bool fg=0;
        int x=rt<<1,y=rt<<1|1;
        if(p.f[dim]>=date[rt].f[dim])swap(x,y);
        if(vis[x])query(p,m,x,dep+1);
        if(q.size()<m)q.push(cur),fg=1;
        else
        {
            if(cur.fi<q.top().fi)
            {
                q.pop();q.push(cur);
            }
            if((p.f[dim]-date[rt].f[dim])*(p.f[dim]-date[rt].f[dim])<q.top().fi)fg=1;
        }
        if(vis[y]&&fg)query(p,m,y,dep+1);
    }
}kd;
int main()
{
    while(scanf("%d%d",&n,&k)!=EOF)
    {
        for(int i=0;i<n;i++)
            for(int j=0;j<k;j++)
                scanf("%d",&a[i].f[j]);
        kd.build(0,n-1,1,0);
        int t;scanf("%d",&t);
        while(t--)
        {
            node p;
            for(int i=0;i<k;i++)scanf("%d",&p.f[i]);
            int m;scanf("%d",&m);
            while(!q.empty())q.pop();
//            printf("%d\n",idx);
            kd.query(p,m,1,0);
            printf("the closest %d points are:\n",m);
            node ans[25];
            for(int i=0;!q.empty();i++)ans[i]=q.top().se,q.pop();
            for(int i=m-1;i>=0;i--)
                for(int j=0;j<k;j++)
                    printf("%d%c",ans[i].f[j],j==k-1?'\n':' ');
        }
    }
    return 0;
}
/***********************

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