HDU1007最近点对（分治）

http://acm.hdu.edu.cn/showproblem.php?pid=1007

 

直接见代码吧。不过这个是N*logN*logN的

尽管如此，我怎么感觉我的比他们的还快？？？

 

  1 #include <map>
  2 #include <set>
  3 #include <stack>
  4 #include <queue>
  5 #include <cmath>
  6 #include <ctime>
  7 #include <vector>
  8 #include <cstdio>
  9 #include <cctype>
 10 #include <cstring>
 11 #include <cstdlib>
 12 #include <iostream>
 13 #include <algorithm>
 14 using namespace std;
 15 #define INF 0x3f3f3f3f
 16 #define mem0(a) memset(a,0,sizeof(a))
 17 #define mem1(a) memset(a,-1,sizeof(a))
 18 #define lson k<<1, L, mid
 19 #define rson k<<1|1, mid+1, R
 20 
 21 //typedef long long LL;
 22 const double eps = 1e-12;
 23 const int MAXN = 100005;
 24 const int MAXM = 500005;
 25 
 26 double min(double a, double b) { return a < b ? a : b; }
 27 
 28 struct Point
 29 {
 30     double x;
 31     double y;
 32 };
 33 int numOfPoint;
 34 Point points[MAXN], TempMerge[MAXN];
 35 Point ansPoint1, ansPoint2;
 36 double closest;
 37 
 38 void initPoints()
 39 {
 40     mem0(points); closest = INF;
 41     for(int i=0;i<numOfPoint;i++)
 42     {
 43         scanf("%lf %lf", &points[i].x, &points[i].y);
 44     }
 45 }
 46 
 47 int cmp_X(Point A, Point B)
 48 {
 49     if(A.x != B.x) return A.x < B.x;
 50     return A.y < B.y;
 51 }
 52 
 53 int cmp_Y(Point A, Point B)
 54 {
 55     if(A.y != B.y) return A.y < B.y;
 56     return A.x < B.x;
 57 }
 58 #define distance(A, B) sqrt((A.x-B.x)*(A.x-B.x)+(A.y-B.y)*(A.y-B.y))
 59 //double distance(Point &A, Point &B)
 60 //{
 61 //    return sqrt((A.x-B.x)*(A.x-B.x)+(A.y-B.y)*(A.y-B.y));
 62 //}
 63 
 64 double calculateTheClosest(int low, int high)
 65 {
 66     for(int i=low;i<=high;i++)TempMerge[i-low] = points[i];
 67     sort(TempMerge, TempMerge+(high-low+1), cmp_Y);
 68     for(int i=0;i<high-low;i++)
 69     {
 70         for(int j=i+1;j<=i+6 && j<=high-low;j++)
 71         {
 72             double calc = distance(TempMerge[i], TempMerge[j]);
 73             if(calc < closest)
 74             {
 75                 closest = calc;
 76                 ansPoint1 = TempMerge[i];
 77                 ansPoint2 = TempMerge[j];
 78             }
 79         }
 80     }
 81     return closest;
 82 }
 83 
 84 double findTheClosest(int left, int right)
 85 {
 86     if(left>=right) return INF;
 87     int mid = (left+right)>>1;
 88     double leftAns = findTheClosest(left, mid);
 89     double rightAns = findTheClosest(mid+1, right);
 90     double ans = min(leftAns, rightAns);
 91     int low = left, high = mid+1;
 92     while(distance(points[low], points[mid])>ans)low++;
 93     while(high <= right && distance(points[high], points[mid])<=ans)high++;
 94     ans = min(ans, calculateTheClosest(low, high-1));
 95     return ans;
 96 }
 97 
 98 int main()
 99 {
100     while(scanf("%d", &numOfPoint) == 1 && numOfPoint)
101     {
102         initPoints();
103         sort(points, points+numOfPoint, cmp_X);
104         double ans = findTheClosest(0, numOfPoint-1);
105         printf("%.2lf\n", ans/2);
106         //printf("The Point(%.2lf, %.2lf) and Point(%.2lf, %.2lf) is %lf\n", ansPoint1.x,ansPoint1.y,ansPoint2.x,ansPoint2.y,ans);
107     }
108     return 0;
109 }

 

posted @ 2014-03-09 20:18  再见~雨泉  阅读(1954)  评论(1)  编辑  收藏  举报