平面最小点对 模板（hdu1007 uva10245）

#include<bits/stdc++.h>using namespace std;typedef long long ll;const int INF=0x3f3f3f3f;struct node1{    double x,y;}node[100010];int cmpx(node1 p1,node1 p2){    return p1.x<p2.x;}int cmpy(node1 p1,node1 p2){    return p1.y<p2.y;}double dis(int x,int y){    return sqrt((node[x].x-node[y].x)*(node[x].x-node[y].x)+(node[x].y-node[y].y)*(node[x].y-node[y].y));}double solve(int a,int b){    if(a+1==b)        return dis(a,b);    if(a==b)        return INF*1.0;    int mid=(a+b)/2;    double d=min(solve(a,mid),solve(mid+1,b));    int l=mid,r=mid;    int flag1=0;    int flag2=0;    while(l>=a&&d>node[mid].x-node[l].x)    {        flag1=1;        l--;    }    while(r<=b&&d>node[r].x-node[mid].x)    {        flag2=1;        r++;    }    if(flag1)        l=l+1;    if(!flag2)        r=r+1;    sort(node+l+1,node+r,cmpy);    for(int i=l+1;i<r-1;i++)        for(int j=i+1;j<r&&node[j].y-node[i].y<d;j++)        {            d=min(dis(i,j),d);        }    return d;}int main(){    int n;    while(scanf("%d",&n)!=EOF&&n)    {        for(int i=0;i<n;i++)            scanf("%lf%lf",&node[i].x,&node[i].y);        sort(node,node+n,cmpx);        printf("%.2f\n",solve(0,n-1)/2);    }    return 0;}