CSUOJ 1549 Navigition Problem

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 1100;
 4 int n;
 5 double R;
 6 struct Point {
 7     double x,y;
 8 } p[maxn];
 9 double getDis(const Point &a,const Point &b) {
10     double tmp = (a.x - b.x)*(a.x - b.x);
11     tmp += (a.y - b.y)*(a.y - b.y);
12     return sqrt(tmp);
13 }
14 vector<Point>ans;
15 int main() {
16     while(~scanf("%d %lf",&n,&R)) {
17         for(int i = 0; i <= n; ++i)
18             scanf("%lf %lf",&p[i].x,&p[i].y);
19         int low = 0,high = n;
20         Point now = p[low++];
21         ans.clear();
22         double hg = 0;
23         while(low <= high) {
24             double ds = getDis(now,p[low]);
25             if((ds - R + hg) > 1e-60) {
26                 now.x += (p[low].x - now.x)/ds*(R-hg);
27                 now.y += (p[low].y - now.y)/ds*(R-hg);
28                 hg += R - hg;
29             }else{
30                 hg += ds;
31                 now = p[low++];
32             }
33             if(fabs(hg - R) < 1e-12) {
34                 ans.push_back(now);
35                 hg = 0.0;
36             }
37         }
38         if(ans.size()) {
39             for(int i = 0; i < ans.size(); ++i)
40                 printf("%.2f,%.2f\n",ans[i].x,ans[i].y);
41         } else puts("No Such Points.");
42     }
43     return 0;
44 }