最近点对问题 HDU Quoit Design 1007 分治法

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<stack>
#include<string>
#include<queue>
using namespace std;
const int maxn =  100005;
const long long INF =  0xfffffff;
struct Point
{
    double x, y;
}P[maxn], Temp[maxn];
bool cmp(Point a, Point b)
{
    if(a.x != b.x)
        return  a.x < b.x;
    return a.y < b.y;
}
bool cmpy(Point a, Point b)
{
    return a.y < b.y;
}
double dis(Point a, Point b)
{
    return sqrt( (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y) );
}
double Colosest(int L,int R)
{
    if(L == R)
        return INF;
    if(L + 1 == R)
        return dis(P[L],P[R]);
    int Mid = (L + R) / 2;
    double d1 = Colosest(L, Mid);
    double d2 = Colosest(Mid + 1, R);

    double  d = min(d1, d2);
//递归找左右两侧的点，最小距离
    int k = 0;

    for(int i = Mid; i >= L; i--)
    {
        if( P[Mid].x - P[i].x < d )
            Temp[k++] = P[i];
        else
            break;
    }

    for(int j = Mid + 1; j <= R; j++)
    {
        if(P[j].x - P[Mid].x < d)
            Temp[k++] = P[j];
        else
            break;
    }
//找出在中间点的可能点对 然后排序
    sort(Temp,Temp+k,cmpy);

    for(int i=0; i<k; i++)
    {
/*需要一个 Temp[j].y - Temp[i].y < d  优化， 不然会超时*/
        for(int j=i+1; j < k && Temp[j].y - Temp[i].y < d ; j++)
        {
            double d3 = dis(Temp[j], Temp[i]);
            if(d3 < d)
                d = d3;
        }
    }
    return d;
}
int main()
{
    int n;
    while(scanf("%d",&n) ,n)
    {
        for(int i=0; i<n; i++)
            scanf("%lf%lf",&P[i].x,&P[i].y);
        sort(P,P+n,cmp);//先排序
        printf("%.2lf\n", Colosest(0,n-1)/2 );
    }
    return 0;
}