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Telescope
Time Limit: 1000MS
Memory Limit: 65536K
Total Submissions: 1178
Accepted: 308
Description
Updog is watching a plane object with a telescope. The field of vision in the telescope can be described as a circle. The center is at the origin and the radius is R. The object can be seen as a simple polygon of N vertexes. Updog wants to know the area of the part of the object that can be seen in the telescope.
Input
The input will contain several test cases. For each case:
The first line contains only one real number R.
The second line contains an integer N. The following N lines contain two real numbers xi and yi each, which describe the coordinates of a vertex. Two vertexes in adjacent lines are also adjacent on the polygon.
Constraints: 3 ≤ N ≤50, 0.1 ≤ R ≤1000, -1000 ≤ xi, yi ≤ 1000
Output
For each test case, output one real number on a separate line, which is the area of the part that can be seen. The result should be rounded to two decimal places.
Sample Input
10 3 0 20 10 0 -10 0
Sample Output
144.35
Source
8994621 | GZHU1006100106 | 3675 | Accepted | 224K | 0MS | C++ | 2887B | 2011-07-25 15:52:39 |
#include <iostream> #include <cmath> using namespace std; #define MAXI 0x400 #define sq(x) ((x) * (x)) #define sng(x) (x == 0.0? 0.0: (x > 0? 1.0: -1.0)) #define fmax(x, y) (x > y? x: y) #define fmin(x, y) (x < y? x: y) struct pt { double x, y; pt(double a = 0, double b = 0) { x = a; y = b; } double len() { return sqrt(sq(x) + sq(y)); } double operator * (pt o) { return x * o.y - o.x * y; } double operator % (pt o) { return x * o.x + y * o.y; } } ps[MAXI]; struct sg { pt a, b; double A, B, C; sg(pt x, pt y) { a = x; b = y; A = a.y - b.y; B = b.x - a.x; C = -(a.y * B + a.x * A); } bool ons(pt o) { if (fmin(a.x, b.x) <= o.x && o.x <= fmax(a.x, b.x)) if (fmin(a.y, b.y) <= o.y && o.y <= fmax(a.y, b.y)) return 1; return 0; } double len() { return sqrt(sq(a.x - b.x) + sq(a.y - b.y)); } double ang() { return acos((a % b) / (a.len() * b.len())); } pt inr(sg o) { double d = (A * o.B - o.A * B); double x = B * o.C - o.B * C; double y = A * o.C - o.A * C; return pt(x / d, -y / d); } }; double r; int n; double TGL(pt a, pt b) //Triangulate { #if 0 printf("a = [%.2lf, %.2lf], b = [%.2lf, %.2lf]\n", a.x, a.y, b.x, b.y); putchar('\n'); #endif double sn = sng(a * b); if (a.len() < b.len()) swap(a ,b); pt lp(a.x - b.x, a.y - b.y), np(-lp.y, lp.x), cp; sg l(a, b), nl(pt(0, 0), np); pt tp = l.inr(nl); double tsu = 0; double oa = a.len(); double ob = b.len(); double ol = tp.len();; double ang, d; if (oa == 0.0 || oa == 0.0 || ol == 0.0) return 0.0; if (oa <= r && ob <= r) { tsu += fabs(a * b / 2.0); #if 0 printf("stu 1"); putchar('\n'); #endif } else if (oa > r && ob <= r) { d = sqrt(sq(r) - sq(tp.len())) / l.len(); tp = pt(tp.x + lp.x * d, tp.y + lp.y * d); ang = sg(a, tp).ang(); tsu += ang * sq(r) / 2.0; tsu += fabs(tp * b/ 2.0); #if 0 printf("stu 2"); printf("tp = [%.2lf, %.2lf]\n", tp.x, tp.y); printf("part1 : %.2lf part2 %.2lf\n", ang * sq(r) / 2.0, fabs(tp * b/ 2.0)); putchar('\n'); #endif } else { ang = acos(ol / r); tsu += l.ang() * sq(r) / 2.0; if (oa > r && ob > r && ol < r && l.ons(tp)) tsu += ol * r * sin(ang) - ang * sq(r); #if 0 printf("stu 3\n"); printf("%.2lf\n", acos(ol / r)); printf("part1 : %.2lf part2 %.2lf\n", l.ang() * sq(r) / 2.0, ol * r * sin(ang) - ang * sq(r)); putchar('\n'); #endif } #if 0 printf("tsu = %.2lf\n\n", tsu * sn); #endif return tsu * sn; } int main() { int i; double tsu; while (scanf("%lf", &r) != EOF) { scanf("%d", &n); for (i = 0; i < n; i++) scanf("%lf%lf", &ps[i].x, &ps[i].y); tsu = 0.0; for (i = 0; i < n; i++) tsu += TGL(ps[i], ps[(i + 1) % n]); printf("%.2lf\n", fabs(tsu)); } return 0; }
发表评论
-
HDU 1058 Humble Numbers
2011-08-02 15:55 1216Humble Numbers Time Limit: 200 ... -
HDU 2095 find your present (2)
2011-08-02 16:13 813find your present (2) Time Lim ... -
HDU 1022 Train Problem I
2011-08-02 21:00 1012Train Problem I Time Limit: 20 ... -
2142 HDU box
2011-08-02 21:21 761box Time Limit: 3000/1000 MS ( ... -
HDU 2151 Worm
2011-08-01 20:48 842Worm Time Limit: 1000/1000 MS ... -
HDU 2722 Here We Go(relians) Again
2011-08-02 00:06 1025Here We Go(relians) Again Time ... -
HDU 3791 二叉搜索树
2011-08-02 14:26 1207二叉搜索树 Time Limit: 20 ... -
PKU 2352 Stars
2011-07-31 21:47 1024Stars Time Limit: 1000MS ... -
PKU 2774 Long Long Message
2011-07-31 21:26 901Long Long Message Time Li ... -
PKU 2777 Count Color
2011-07-31 21:31 793Count Color Time Limit: 1 ... -
HDU 2098 分拆素数和
2011-07-31 21:08 1061分拆素数和 Time Limit: 1000/1000 MS ... -
ZOJ 3512 Financial Fraud .
2011-07-31 20:49 1279Financial Fraud Time Limit: 3 ... -
HDU 1798 Tell me the area .
2011-07-31 20:47 1119Tell me the area Time Limit: 3 ... -
HDU 2962 Trucking .
2011-07-31 20:46 679Trucking Time Limit: 20000/100 ... -
HDU 1596 find the safest road .
2011-07-31 20:45 601find the safest road Time Limi ... -
HDU 2553 N皇后问题 .
2011-07-31 20:20 702N皇后问题 Time Limit: 2000/1000 MS ... -
HDU 1392 Surround the Trees .
2011-07-31 20:19 793Surround the Trees Time Limit: ... -
HDU 1234 开门人和关门人 .
2011-07-31 20:17 671开门人和关门人 Time Limit: 2000/1000 ... -
HDU 1174 爆头 .
2011-07-31 20:16 611爆头 Time Limit: 2000/1000 M ... -
HDU 1316 How Many Fibs? .
2011-07-31 20:15 975How Many Fibs? Time Limit: 200 ...
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