poj2420A Star not a Tree?(模拟退火）

链接

求某一点到其它点距离和最小，求这个和，这个点 为费马点。

做法：模拟退火

 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 100000

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

21 }p[N];

22 int n;

23 int dir[4][2] = {0,1,0,-1,1,0,-1,0};

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)

30 {

31     return sqrt(a.x*a.x+a.y*a.y);

32 }

33 double cal(point pp)

34 {

35     int i;

36     double s = 0;

37     for(i = 1; i <= n; i++)

38     s+=dis(pp-p[i]);

39     return s;

40 }

41 int main()

42 {

43     int i;

44     while(scanf("%d",&n)!=EOF)

45     {

46         double t = 10000;

47         point pp = point(0,0);

48         for(i =1 ; i <= n;i ++)

49         {

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

51             pp.x+=p[i].x;

52             pp.y+=p[i].y;

53         }

54         pp.x /=n;

55         pp.y /=n;

56         double sum = cal(pp),tmp;

57         point tp,ans = pp;

58         while(t>0.02)

59         {

60             int flag = 1;

61             while(flag)

62             {

63                 flag = 0;

64                 for(i =0 ; i< 4 ; i++)

65                 {

66                     tp = point(pp.x+dir[i][0]*t,pp.y+dir[i][1]*t);

67                     tmp = cal(tp);

68                     if(tmp<sum)

69                     {

70                         sum = tmp;

71                         flag = 1;

72                         ans = tp;

73                     }

74                 }

75                 pp = ans;

76             }

77             t/=2;

78         }

79         printf("%.0f\n",sum);

80     }

81     return 0;

82 }

View Code