Beauty Contest

直接跑一個凸包，然后跑一跑旋轉卡殼，求最大值就行了。

/*Author : lifehappy */ #include <cstdio> #include <cmath> #include <cstring> #include <algorithm> #include <vector> #include <iostream>using namespace std;const double pi = acos(-1.0); const double eps = 1e-5; const double inf = 1e100;int Sgn(double x) {return x < -eps ? -1 : x > eps; }struct Vector {double x, y;bool operator < (Vector &a) const {return x < a.x;}void print() {printf("%f %f\n", x, y);}void read() {scanf("%lf %lf", &x, &y);}Vector(double _x = 0, double _y = 0) : x(_x), y(_y) {}double mod() {return sqrt(x * x + y * y);}double mod2() {return x * x + y * y;}Vector operator + (const Vector &a) {return Vector(x + a.x, y + a.y);}Vector operator - (const Vector &a) {return Vector(x - a.x, y - a.y);}double operator * (const Vector &a) {return x * a.x + y * a.y;}double operator ^ (const Vector &a) {return x * a.y - y * a.x;}Vector Rotate(double angle) {return Vector(x * cos(angle) - y * sin(angle), x * sin(angle) + y * cos(angle));}Vector operator << (const double &a) {return Vector(x * a, y * a);}Vector operator >> (const double &a) {return Vector(x / a, y / a);}bool operator == (const Vector & a) {return (Sgn(x - a.x) == 0) && (Sgn(y - a.y) == 0);} };typedef Vector Point;double Dis_pp(Point a, Point b) {return sqrt((a - b) * (a - b)); }double Angle(Vector a, Vector b) {//[0, 2pi)double ans = atan2(a ^ b, a * b);return ans < 0 ? ans + 2 * pi : ans;// return atane(a ^ b, a * b); }double To_lefttest(Point a, Point b, Point c) {return (b - a) ^(c - a); }int Toleft_test(Point a, Point b, Point c) {return Sgn((b - a) ^ (c - a)); }struct Line {Point st, ed;Line(Point _st = Point(0, 0), Point _ed = Point(0, 0)) : st(_st), ed(_ed) {}bool operator < (const Line &t) {return st.x < t.st.x;}void read() {scanf("%lf %lf %lf %lf", &st.x, &st.y, &ed.x, &ed.y);} };bool Parallel(Line a, Line b) {return Sgn((a.st - a.ed) ^ (b.st - b.ed)) == 0; }bool Is_cross(Line a, Line b) {return Toleft_test(a.st, a.ed, b.st) * Toleft_test(a.st, a.ed, b.ed) <= 0 && Toleft_test(b.st, b.ed, a.st) * Toleft_test(b.st, b.ed, a.ed) <= 0; }Point Cross_point(Line a, Line b) {if(!Is_cross(a, b)) {return Point(inf, inf);}else {double a1 = fabs(To_lefttest(a.st, a.ed, b.st)), a2 = fabs(To_lefttest(a.st, a.ed, b.ed));return ((b.st << a2) + (b.ed << a1)) >> (a1 + a2);} }Point Intersect_point(Line a, Line b) {double a1 = a.st.y - a.ed.y, b1 = a.ed.x - a.st.x, c1 = a.st.x * a.ed.y - a.ed.x * a.st.y;double a2 = b.st.y - b.ed.y, b2 = b.ed.x - b.st.x, c2 = b.st.x * b.ed.y - b.ed.x * b.st.y;return Point((c1 * b2 - c2 * b1) / (a2 * b1 - a1 * b2), (a2 * c1 - a1 * c2) / (a1 * b2 - a2 * b1)); }Point Shadow(Line a, Point b) {Point dir = a.ed - a.st;return a.st + (dir << (((b - a.st) * dir) / dir.mod2())); }Point Reflect(Line a, Point b) {return (Shadow(a, b) << 2) - b; }bool inmid(double a, double b, double x) {if(a > b) swap(a, b);return Sgn(x - a) >= 0 && Sgn(b - x) >= 0; }bool Point_in_line(Line a, Point b) {if(Toleft_test(a.st, a.ed, b) != 0) return false;return inmid(a.st.x, a.ed.x, b.x) && inmid(a.st.y, a.ed.y, b.y); }double Dis_lp(Line a, Point b) {Point h = Shadow(a, b);if(Point_in_line(a, h)) {return Dis_pp(h, b);}return min(Dis_pp(a.st, b), Dis_pp(a.ed, b)); }// double Dis_ll(Line a, Line b) { // if(Is_cross(a, b)) return 0; // return min({Dis_lp(a, b.st), Dis_lp(a, b.ed), Dis_lp(b, a.st), Dis_lp(b, a.ed)}); // }double Area(vector<Point> p, int n) {double ans = 0;for(int i = 0; i < n; i++) {ans += p[i] ^ p[(i + 1) % n];}return 0.5 * ans; }double len(vector<Point> p, int n) {double ans = 0;for(int i = 0; i < n; i++) {ans += Dis_pp(p[i], p[(i + 1) % n]);}return ans; }bool Is_convex(Point *a, int n) {bool flag[3] = {0, 0, 0};for(int i = 0; i < n; i++) {flag[Sgn(To_lefttest(a[i], a[(i + 1) % n], a[(i + 2) % n])) + 1] = true;if(flag[0] && flag[2]) return false;}return true; }Point p0;bool cmp_graham(Point a, Point b) {int flag = Toleft_test(p0, a, b);return flag == 0 ? Dis_pp(p0, a) < Dis_pp(p0, b) : flag > 0; }vector<Point> Graham(vector<Point> &a, int n) {p0 = a[0];for(int i = 0; i < n; i++) {if(a[i].y < p0.y || (a[i].y == p0.y && a[i].x < p0.x)) {p0 = a[i];}}vector<Point> ans;sort(a.begin(), a.end(), cmp_graham);if(n == 1) {ans.push_back(a[0]);return ans;}if(n == 2) {ans.push_back(a[0]);ans.push_back(a[1]);return ans;}ans.push_back(a[0]);ans.push_back(a[1]);int sz = 2;for(int i = 2; i < n; i++) {while(sz > 1 && To_lefttest(ans[sz - 2], ans[sz - 1], a[i]) <= 0) {ans.pop_back();sz--;}ans.push_back(a[i]);sz++;}return ans; }bool cmp_andrew(Point a, Point b) {if(Sgn(a.x - b.x) == 0) return a.y < b.y;return a.x < b.x; }vector<Point> Andrew(vector<Point> &a, int n) {sort(a.begin(), a.end(), cmp_andrew);int p1 = 0, p2;vector<Point> ans;for(int i = 0; i < n; i++) {while(p1 > 1 && Toleft_test(ans[p1 - 2], ans[p1 - 1], a[i]) <= 0) ans.pop_back(), p1--;ans.push_back(a[i]), p1++;}p2 = p1;for(int i = n - 2; i>= 0; i--) {while(p2 > p1 && Toleft_test(ans[p2 - 2], ans[p2 - 1], a[i]) <= 0) ans.pop_back(), p2--;ans.push_back(a[i]), p2++;}ans.pop_back();return ans; }double Get_angle(Line a) {return atan2(a.ed.y - a.st.y, a.ed.x - a.st.x); }bool cmp_Half_lane_intersection(Line a, Line b) {Vector va = a.ed - a.st, vb = b.ed - b.st;double A = Get_angle(va), B = Get_angle(vb);if (Sgn(A - B) == 0) return Sgn(((va) ^ (b.ed - a.st))) != -1;return Sgn(A - B) == -1; }bool On_right(Line a, Line b, Line c) {Point o = Intersect_point(b, c);if (Sgn((a.ed - a.st) ^ (o - a.st)) < 0) return true;return false; }const int N = 2e3 + 10;Line que[N];double Half_lane_intersection(vector<Line> &a) {sort(a.begin(), a.end(), cmp_Half_lane_intersection);int head = 0, tail = 0, cnt = 0, n = a.size();for(int i = 0; i < n - 1; i++) {if(Sgn(Get_angle(a[i]) - Get_angle(a[i + 1])) == 0) continue;a[cnt++] = a[i];}a[cnt++] = a[n - 1];for(int i = 0; i < cnt; i++) {while(tail - head > 1 && On_right(a[i], que[tail - 1], que[tail - 2])) tail--;while(tail - head > 1 && On_right(a[i], que[head], que[head + 1])) head++;que[tail++] = a[i];}while(tail - head > 1 && On_right(que[head], que[tail - 1], que[tail - 2])) tail--;while(tail - head > 1 && On_right(que[tail - 1], que[head], que[head + 1])) head++;n = tail - head;if(n < 3) return 0;vector<Point> ans;for(int i = head; i < tail; i++) {ans.push_back(Intersect_point(que[i], que[(i - head + 1) % n + head]));}return fabs(Area(ans, ans.size())); }double RotateCalipers(vector<Point> a, int n) {double ans = 0; int now = 1;a.push_back(a[0]);for(int i = 0; i < n; i++){while(((a[now] - a[i + 1]) ^ (a[i] - a[i + 1])) < ((a[now + 1] - a[i + 1]) ^ (a[i] - a[i + 1]))) now = (now + 1) % n;ans = max(ans, max((a[now] - a[i]) * (a[now] - a[i]), (a[now] - a[i + 1]) * (a[now] - a[i + 1])));}return ans; }int main() {// freopen("in.txt", "r", stdin);// freopen("out.txt", "w", stdout);// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);int n;vector<Point> a;scanf("%d", &n);for(int i = 1; i <= n; i++) {Point temp;temp.read();a.push_back(temp);}a = Andrew(a, a.size());printf("%lld\n", (long long)(RotateCalipers(a, a.size())) );return 0; }

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