POJ 2402- A Star not a Tree?(费马点)

Tue, 31 Mar 2009 04:08:00 GMT

  1#include <cstdio>
  2#include <cmath>
  3
  4const int SIZE = 102;
  5
  6struct TPoint
  7{
  8    double x ;
  9    double y ;
10} ;
11
12TPoint point[SIZE];
13int N;
14
15double Distance( const TPoint& p1, const TPoint& p2 )
16{
17    return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y)) ;
18}
19
20double GetALLDist( const TPoint& p, const int& n )
21{
22    int i;
23    double sum = 0.0;
24
25    for ( i = 0; i < n; ++i )
26        sum += Distance( p, point[i] );
27
28    return sum;
29}
30
31double GetFermatPoint( const int& n )
32{
33    TPoint st = point[0];
34    TPoint tmp, nt;
35    double t, step = 100, fermat = GetALLDist(st, n);
36
37    while ( step > 0.2 )
38    {
39        int ok = 1;
40
41        while ( ok ) {
42            ok = 0;
43            nt = st;
44
45            tmp.x = st.x, tmp.y = st.y + step;
46
47            t = GetALLDist(tmp, n);
48
49            if ( t < fermat )
50            {
51                fermat = t;
52                ok = 1;
53                nt = tmp;
54            }
55
56            tmp.x = st.x, tmp.y = st.y - step;
57
58            t = GetALLDist(tmp, n);
59            if ( t < fermat )
60            {
61                fermat = t;
62                ok = 1;
63                nt = tmp;
64            }
65
66            tmp.x = st.x + step, tmp.y = st.y;
67
68            t = GetALLDist(tmp, n);
69
70            if ( t < fermat )
71            {
72                fermat = t;
73                ok = 1;
74                nt = tmp;
75            }
76
77            tmp.x = st.x - step, tmp.y = st.y;
78
79            t = GetALLDist(tmp, n);
80            if ( t < fermat )
81            {
82                fermat = t;
83                ok = 1;
84                nt = tmp;
85            }
86
87            st = nt;
88        }
89
90        step /= 2.0;
91    }
92
93    return fermat;
94}
95
96int main()
97{
98    int i, ans;
99    double t;
100
101    scanf("%d", &N);
102
103    for ( i = 0; i < N; ++i )
104    {
105        scanf("%lf %lf", &point[i].x, &point[i].y);
106    }
107
108    t = GetFermatPoint( N );
109
110    ans = (int)(t + 0.5) * 100 / 100;
111
112    printf("%d\n", ans);
113
114    return 0;
115}

巫 2009-03-31 12:08 发表评论

C++博客-gzwzm06-文章分类-几何

POJ 2402- A Star not a Tree?(费马点)