【HDOJ】1348 Wall
计算几何-凸包模板题目，Graham算法解。
1 /* 1348 */ 2 #include <iostream> 3 #include <cstdio> 4 #include <cstring> 5 #include <cstdlib> 6 #include <cmath> 7 #include <algorithm> 8 using namespace std; 9 10 #define MAXN 1005 11 12 typedef struct Point_t { 13 double x, y; 14 Point_t() {} 15 Point_t(double xx, double yy) { 16 x = xx; y = yy; 17 } 18 } Point_t; 19 20 Point_t stack[MAXN]; 21 Point_t points[MAXN]; 22 const double PI = acos(-1.0); 23 int n; 24 25 double Length(Point_t a, Point_t b) { 26 return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y)); 27 } 28 29 double cross(Point_t p0, Point_t p1, Point_t p2) { 30 return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y); 31 } 32 33 bool comp(Point_t a, Point_t b) { 34 double k = cross(points[0], a, b); 35 return !(k<0 || (k==0 && Length(points[0], a)>Length(points[0], b))); 36 } 37 38 double Graham() { 39 double ret = 0; 40 int i, j, k; 41 int top; 42 Point_t p0; 43 44 p0 = points[0]; 45 k = 0; 46 for (i=1; i<n; ++i) { 47 if (points[i].x<p0.x || (points[i].x==p0.x && points[i].y<p0.y)) { 48 p0 = points[i]; 49 k = i; 50 } 51 } 52 53 points[k] = points[0]; 54 points[0] = p0; 55 sort(points+1, points+n, comp); 56 57 stack[0] = points[0]; 58 stack[1] = points[1]; 59 stack[2] = points[2]; 60 top = 2; 61 for (i=3; i<n; ++i) { 62 while (cross(stack[top-1], stack[top], points[i])<=0 && top>1) 63 --top; 64 stack[++top] = points[i]; 65 } 66 stack[++top] = p0; 67 for (i=1; i<=top; ++i) 68 ret += Length(stack[i-1], stack[i]); 69 70 return ret; 71 } 72 73 int main() { 74 int t; 75 int i, j, k, tmp; 76 double l, ans; 77 78 #ifndef ONLINE_JUDGE 79 freopen("data.in", "r", stdin); 80 #endif 81 82 scanf("%d", &t); 83 while (t--) { 84 scanf("%d %lf", &n, &l); 85 for (i=0; i<n; ++i) 86 scanf("%lf %lf", &points[i].x, &points[i].y); 87 ans = Graham(); 88 ans += PI * (l+l); 89 printf("%.0lf\n", ans); 90 if (t) 91 printf("\n"); 92 } 93 94 return 0; 95 }
