poj3714Raid(平面最近点对）

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  1 #include <iostream>

  2 #include<cstdio>

  3 #include<cstring>

  4 #include<algorithm>

  5 #include<stdlib.h>

  6 #include<vector>

  7 #include<cmath>

  8 #include<queue>

  9 #include<set>

 10 using namespace std;

 11 #define N 200010

 12 #define LL long long

 13 #define INF 0xfffffff

 14 const double eps = 1e-8;

 15 const double pi = acos(-1.0);

 16 const double inf = ~0u>>2;

 17 struct point

 18 {

 19     double x,y;

 20     int id;

 21     int flag;

 22     point(double x=0,double y =0):x(x),y(y){}

 23 }p[N],pp[N],py[N];

 24 typedef point pointt;

 25 pointt operator -(point a,point b)

 26 {

 27     return point(a.x-b.x,a.y-b.y);

 28 }

 29 double dis(point a,point b)

 30 {

 31     if(a.flag==b.flag) return INF;

 32     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

 33 }

 34 bool cmp(point a,point b)

 35 {

 36     return a.x<b.x;

 37 }

 38 bool cmpp(point a,point b)

 39 {

 40     return a.y<b.y;

 41 }

 42 void binmerge(point py[],point pp[],int l,int m,int r)

 43 {

 44     int i,j,g=l;

 45     for(i = l,j = m+1 ; i <= m&&j <= r ;)

 46     if(pp[i].y<pp[j].y) py[g++] = pp[i++];

 47     else py[g++] = pp[j++];

 48 

 49     while(i<=m) py[g++] = pp[i++];

 50     while(j<=r) py[g++] = pp[j++];

 51     memcpy(pp + l, py + l, (r - l + 1) *sizeof(py[0]));

 52 }

 53 double binshortest(point p[],point pp[],point py[],int l,int r)

 54 {

 55     if(r-l==1) return dis(p[l],p[r]);

 56     if(r-l==2) return min(min(dis(p[l],p[r]),dis(p[l],p[l+1])),dis(p[l+1],p[r]));

 57     int mid = (l+r)>>1;

 58     int i,j,g = l,o = mid+1;

 59     for(i = l ; i <= r ; i++)

 60     {

 61         if(py[i].id<=mid)//按y坐标顺序将点划分到pp左半数组

 62         pp[g++] = py[i];

 63         else

 64         pp[o++] = py[i];//pp右半数组

 65     }

 66     double minz = min(binshortest(p,py,pp,l,mid),binshortest(p,py,pp,mid+1,r));

 67     binmerge(py,pp,l,mid,r);

 68     g = l;

 69     for(i = l ; i <= r ; i++)

 70     if(fabs(py[i].x-py[mid].x)<minz) pp[g++] = py[i];

 71     for(i = l ; i < g ; i++)

 72     {

 73         for(j = i+1 ; j < g && fabs(pp[i].y-pp[j].y)<minz; j++)

 74         minz = min(dis(pp[i],pp[j]),minz);

 75     }

 76     return minz;

 77 }

 78 int main()

 79 {

 80     int n,i,t;

 81     cin>>t;

 82     while(t--)

 83     {

 84         scanf("%d",&n);

 85         for(i = 0; i < n; i++)

 86         {

 87             scanf("%lf%lf",&p[i].x,&p[i].y);

 88             p[i].flag = 1;

 89         }

 90         for(i = n; i < n*2; i++)

 91         {

 92             scanf("%lf%lf",&p[i].x,&p[i].y);

 93             p[i].flag = 2;

 94         }

 95         n<<=1;

 96         sort(p,p+n,cmp);

 97         for(i = 0;i < n ;i++)

 98         p[i].id = i;

 99         memcpy(py,p,n*sizeof(py[0]));

100         sort(p,p+n,cmpp);

101         double ans = binshortest(p,pp,py,0,n-1);

102         printf("%.3f\n",ans);

103     }

104     return 0;

105 }

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