$Poj3714/AcWing Raid$ 分治/平面最近点对

Posted 2022-07-17 forward777

$AcWing$

 

$Sol$

平面最近点对板子题,注意要求的是两种不同的点之间的距离.

 

$Code$

#include<bits/stdc++.h>
#define il inline
#define Rg register
#define go(i,a,b) for(Rg int i=a;i<=b;++i)
#define yes(i,a,b) for(Rg int i=a;i>=b;--i)
#define mem(a,b) memset(a,b,sizeof(a))
#define ll long long
#define db double
#define inf 2100000000
using namespace std;
il int read()

    Rg int x=0,y=1;char c=getchar();
    while(c<‘0‘||c>‘9‘)if(c==‘-‘)y=-1;c=getchar();
    while(c>=‘0‘&&c<=‘9‘)x=(x<<1)+(x<<3)+c-‘0‘;c=getchar();
    return x*y;

int T,n;
struct nodeint x,y;bool tp;a[(int)1e5*2+1],tmp[(int)1e5*2+1];
il bool cmp(node x,node y)if(x.x==y.x)return x.y<y.y;return x.x<y.x;
il bool cmp1(node x,node y)return x.y<y.y;
il ll dis(node x,node y)db xx=x.x-y.x,yy=x.y-y.y;return xx*xx+yy*yy;
il ll sol(int l,int r)

    if(l>r || l==r)return inf;
    if(l+1==r)
    
        if(a[l].tp!=a[r].tp)return dis(a[l],a[r]);
        else return inf;
    
    Rg int mid=(l+r)>>1,ct=0;
    ll mins=min(sol(l,mid),sol(mid+1,r));
    go(i,l,r)if((a[i].x-a[mid].x)*(a[i].x-a[mid].x)<=mins)tmp[++ct]=a[i];
    sort(tmp+1,tmp+ct+1,cmp1);
    go(i,1,ct)
        go(j,i+1,ct)
    
        if((tmp[j].y-tmp[i].y)*(tmp[j].y-tmp[i].y)>mins)break;
        if(tmp[i].tp!=tmp[j].tp)mins=min(mins,dis(tmp[i],tmp[j]));
    
    return mins;

int main()

    T=read();
    while(T--)
    
        n=read();
        go(i,1,n)a[i]=(node)read(),read(),1;
        go(i,1,n)a[i+n]=(node)read(),read(),0;
        sort(a+1,a+n*2+1,cmp);
        printf("%.3lf\\n",sqrt(sol(1,2*n)));
    
    return 0;

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