Simple geometry (convex package) POJ 1113 Wall

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Test instructions: To find the shortest route, so that any point on the line away from the castle at least L distance

Analysis: Convex hull First, answer = length of convex hull + circumference of circle with L as radius

/************************************************* author:running_time* Created time:2015/10/25 11:00:48* File N Ame:P oj_1113.cpp ************************************************/#include <cstdio> #include <algorithm > #include <iostream> #include <sstream> #include <cstring> #include <cmath> #include < string> #include <vector> #include <queue> #include <deque> #include <stack> #include < list> #include <map> #include <set> #include <bitset> #include <cstdlib> #include <ctime >using namespace std; #define Lson L, Mid, RT << 1#define Rson mid + 1, R, RT << 1 | 1typedef long ll;const int N = 1e3 + 10;const int INF = 0x3f3f3f3f;const int MOD = 1e9 + 7;const double EPS = 1e-10;     int dcmp (double x) {///three state function, reduced accuracy problem if (fabs (x) < EPS) return 0; else return x < 0? -1:1;     } struct Point {//points defined by double x, y; Point (Double x=0, double y=0):X (x), Y (y) {} point operator + (const-point &r) const {//Vector addition return point (x + r.x, y + r.y);     } Point operator-(const point &r) const {//Vector subtraction return point (x-r.x, Y-R.Y);     } Point operator * (double p) {///vector multiplied by a scalar return point (x * p, Y * p);     } point operator/(double p) {///vector divided by scalar return point (x/p, y/p); } BOOL operator < (const point &r) const {//DOT coordinate sort return x < R.x | |     (x = = r.x && y < r.y);  } bool operator = = (Const point &r) const {//judgment same dot return dcmp (x-r.x) = = 0 && dcmp (Y-     R.Y) = = 0; } };       typedef point Vector;     Vector definition point read_point (void) {//points read in double x, y;     scanf ("%lf%lf", &x, &y); Return point (x, y);      } double Polar_angle (vector a) {//Vector polar return atan2 (A.Y, a.x);} double dot (vector A, vector B) {//Vectors dot Product Return a.x * b.x +A.Y * B.Y; } Double Cross (vector A, vector B) {//vector fork product return a.x * B.Y-A.Y * b.x;} double length (vector a) {/ /vector length, dot product return sqrt (dot (A, a)); } double angle (vector a, vector b) {//Vector corner, counterclockwise, dot product return ACOs (dot (A, b)/Length (a)/length (b));} Doub Le Area_triangle (Point A, point B, point C) {//triangular area, fork product return Fabs (Cross (b-a, c-a))/2.0;} Vector Rotate (vector A, double rad) {//vector rotation, counterclockwise return vector (a.x * cos (RAD)-A.y * sin (rad), a.x * sin (ra D) + a.y * cos (RAD));     } vector nomal (vector a) {//vector of unit method vector Double len = length (a); Return Vector (-a.y/len, A.x/len);     } point Point_inter (point P, Vector V, point q, Vector W) {//two line intersection, parametric equation Vector U = p-q;     Double T = Cross (w, U)/Cross (V, W); return p + V * t;     Double Dis_to_line (point P, Dot A, point B) {//points to straight line distance, two points Vector V1 = b-a, V2 = p-a; Return Fabs (Cross (V1, V2))/Length (V1); } DOUBLThe distance from {//to the line segment of the E dis_to_seg (point P, Dot a, points b), two-point if (a = = b) return length (P-A);     Vector V1 = b-a, V2 = p-a, V3 = P-b;     if (DCMP (dot (V1, V2)) < 0) return length (V2);     else if (dcmp (dot (V1, V3)) > 0) return length (V3); else return Fabs (cross (V1, V2))/Length (V1);     } point Point_proj (points P, points A, point B) {//dots on the line projection, two-dot Vector V = b-a; Return a + v * (dot (v, p-a)/dot (V, v)); } bool Inter (point A1, O-A2, points B1, bit b2) {//Judgment segment intersection, two-dot double c1 = Cross (A2-A1, b1-a1), C2 =     Cross (A2-A1, b2-a1), C3 = Cross (B2-B1, a1-b1), C4 = Cross (b2-b1, A2-B1); Return DCMP (C1) * DCMP (C2) < 0 && dcmp (C3) * DCMP (C4) < 0; } bool On_seg (point P, Dot A1, point A2) {//Judgment points on the segment, two points return dcmp (cross (a1-p, a2-p)) = = 0 &&am P DCMP (dot (a1-p, a2-p)) < 0; } double Area_poly (point *p, int n) {//Polygon area double ret = 0;     for (int i=1; i<n-1; ++i) {ret + = Fabs (Cross (P[i]-p[0], p[i+1]-p[0])); } return RET/2;    } vector<point> Convex_hull (vector<point> &p) {sort (P.begin (), P.end ());    int n = p.size (), k = 0;    vector<point> ret (n * 2);         for (int i=0; i<n; ++i) {when (K > 1 && Cross (ret[k-1]-ret[k-2], P[i]-ret[k-1]) <= 0) k--;    ret[k++] = P[i]; } for (int i=n-2, t=k; i>=0;-I.) {while (K > t && Cross (Ret[k-1]-ret[k-2], P[i]-ret[k-1])        <= 0) k--;    ret[k++] = P[i];    } ret.resize (k-1);  return ret;}     struct Circle {point C;     Double R; Circle () {} circle (point C, Double R): C (c), R (r) {} "point" (double a) {return point (c.x + Co     S (a) * R, C.y + sin (a) * R); } };     struct line {point P;     Vector v;     Double R;   Line () {} line (const point &p, const Vector &v): P (P), V (v) {      R = Polar_angle (v);     } Point point (Double A) {return P + v * A;     } }; /* Line intersection to find the intersection, return the number of intersections, the intersection is saved in P */int line_cir_inter (lines L, Circle C, double &t1, double &t2, vector<point> & Amp     P) {Double A = l.v.x, B = l.p.x-c.c.x, C = l.v.y, d = l.p.y-c.c.y;     Double E = A * a + c * C, F = 2 * (A * b + c * d), G = b * B + d * D-C.R * C.R;     Double delta = f * f-4 * e * g;     if (dcmp (delta) < 0) return 0; if (dcmp (delta) = = 0) {T1 = t2 =-F/(2 * e);         P.push_back (L.point (t1));     return-1; } T1 = (-f-sqrt (delta))/(2 * e);     P.push_back (L.point (t1)); T2 = (-f + sqrt (delta))/(2 * e);     P.push_back (L.point (T2));     if (dcmp (T1) < 0 | | dcmp (t2) < 0) return 0; return 2; }/* Two circle intersection to find the intersection, return the number of intersections.     The intersection is saved in P */int Cir_cir_inter (Circle C1, Circle C2, vector<point> &p) {Double d = length (c1.c-c2.c); if (dcmp (d) = = 0) {if (dcmp (C1.R-C2.R) = =0) Return-1;     Two circles overlap else return 0;     } if (dcmp (C1.R + c2.r-d) < 0) return 0;     if (dcmp (Fabs (C1.R-C2.R)-D) < 0) return 0;     Double A = Polar_angle (c2.c-c1.c);        Double da = ACOs ((C1.R * C1.R + d * D-C2.R * C2.R)/(2 * C1.R * d));     C1C2 to C1p1 's horn?     Point P1 = C1.point (a-da), p2 = c2.point (A + da);     P.push_back (p1);     if (P1 = = p2) return 1;     else P.push_back (p2); return 2;    }const Double PI = ACOs ( -1.0);vector<point> p;int main (void) {int n;    Double L;        while (scanf ("%d%lf", &n, &l) = = 2) {p.clear ();        for (int i=0; i<n; ++i) {p.push_back (Read_point ());        } vector<point> q = Convex_hull (p);        Double ans = 0;        Q.push_back (Q[0]);        for (int i=0; i<q.size ()-1; ++i) {ans + = length (q[i+1]-q[i]);        } ans + = 2 * PI * L;    printf ("%.0f\n", ans); } return 0;}

Simple geometry (convex package) POJ 1113 Wall