poj3714 Raid

Posted 2021-01-28 dream-runner

平面最近点对，以后再也不用vector了！会t。。。

#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
using namespace std;
const int N=200010;
const double inf=2147483647;
struct node{double x,y;bool k;}a[N],p[N],v[N];
bool cmp(const node&a,const node&b){return a.x<b.x;}
double solve(int l,int r){
    if(l>=r)return inf;
    int mid=(l+r)>>1;
    double ret=min(solve(l,mid-1),solve(mid+1,r)),d=a[mid].x;
    int t1=l,t2=mid+1;
    for(int i=l;i<=r;++i){
        if(t2>r||t1<=mid&&a[t1].y<a[t2].y)p[i]=a[t1],++t1;
        else p[i]=a[t2],++t2;
    }
    int cnt=0;
    for(int i=l;i<=r;++i){
        if(fabs(a[i].x-d)>=ret)continue;
        for(int j=cnt;j>=1;--j){
            if(fabs(a[i].y-v[j].y)>=ret)break;
            if(a[i].k==v[j].k)continue;
            double x1=a[i].x,y1=a[i].y,x2=v[j].x,y2=v[j].y;
            ret=min(ret,sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));        
        }
        v[++cnt]=a[i];
    }
    return ret;
}
int main(){
    int T;
    scanf("%d",&T);
    while(T--){
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;++i){
            scanf("%lf%lf",&a[i].x,&a[i].y);
            a[i].k=0;
        }
        for(int i=1;i<=n;++i){
            scanf("%lf%lf",&a[i+n].x,&a[i+n].y);
            a[i+n].k=1;
        }
        sort(a+1,a+1+2*n,cmp);
        printf("%.3lf
",solve(1,2*n));
    }
    return 0;
}

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