我在算法竞赛从入门到进阶那里看的，通过做题还加了一些函数，觉得不错来看看吧！(有新的函数算法我会持续更新放入，记得来看！)
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
#define N 100005
#define eps 0.00000001//偏差值1e8
#define pi acos(-1.0)//高精度圆周率
const int maxp = 1010; //点的数量
int sgn(double x){ //判断x是否等于0
if (fabs(x) < eps) return 0;
else return x < 0 ? -1 : 1;
}
int Dcmp(double x, double y){ //比较两个浮点数：0为相等；-1为小于；1为大于
if (fabs(x - y) < eps)return 0;
else return x < y ? -1 : 1;
}
//——————————————————平面几何：点和线————————————————————————
struct Point { //定义点及其基本运算
double x, y;
Point() {}
Point(double x, double y) :x(x), y(y) {}
Point operator + (Point B) { return Point(x + B.x, y + B.y); }
Point operator - (Point B) { return Point(x - B.x, y - B.y); }
Point operator * (double k) { return Point(x *k, y * k); } //长度增大k倍
Point operator / (double k) { return Point(x / k, y /k); } //长度缩小k倍
bool operator ==(Point B) { return sgn(x - B.x) == 0 && sgn(y - B.y) == 0; }
bool operator <(Point B) //比较两个点，用于凸包计算
{
return sgn(x - B.x) < 0 || (sgn(x - B.x) == 0 && sgn(y - B.y) < 0);
}
};
typedef Point Vector; //定义向量
double Dot(Vector A, Vector B) { return A.x * B.x + A.y * B.y; } //点积
double Len(Vector A) { return sqrt(Dot(A, A)); } //向量的长度
double Len2(Vector A) { return Dot(A, A); } //向量长度的平方
//A与B的夹角
double Angle(Vector A, Vector B) { return acos(Dot(A, B) / Len(A) / Len(B)); }
double Cross(Vector A, Vector B) { return A.x * B.y - A.y * B.x; } //叉积
//三角形ABC面积的两倍
double Area2(Point A, Point B, Point C) { return Cross(B - A, C - A); }
//两点的距离，用两种方式实现
double Distance(Point A, Point B) { return hypot(A.x - B.x, A.y - B.y); }
double Dist(Point A, Point B){
return sqrt((A.x - B.x) * (A.x - B.x) + (A.y - B.y) * (A.y - B.y));
}
//向量A的单位法向量
Vector Normal(Vector A) { return Vector(-A.y / Len(A), A.x / Len(A)); }
//向量是否平行或重合
bool Parallel(Vector A, Vector B) { return sgn(Cross(A, B)) == 0; }
Vector Rotate(Vector A, double rad) { //向量A逆时针旋转rad度
return Vector(A.x * cos(rad) - A.y * sin(rad), A.x * sin(rad) + A.y * cos(rad));
}
struct Line { //线上的两个点
Point p1, p2;
Line(){}
Line(Point p1,Point p2):p1(p1),p2(p2){}
//根据一个点和倾斜角angle确定直线，0≤angle<pi
Line(Point p, double angle)
{
p1 = p;
if (sgn(angle - pi / 2) == 0) { p2 = (p1 + Point(0, 1)); }
else { p2 = (p1 + Point(1, tan(angle))); }
}
//ax+by+c=0
Line(double a, double b, double c) {
if (sgn(a) == 0) {
p1 = Point(0, -c / b);
p2 = Point(1, -c / b);
}
else if (sgn(b) == 0) {
p1 = Point(-c / a, 0);
p2 = Point(-c / a, 1);
}
else {
p1 = Point(0, -c / b);
p2 = Point(1, (-c - a) / b);
}
}
};
typedef Line Segment; //定义线段，两端点是Point p1,p2
//返回直线倾斜角，0≤angle<pi
double Line_angle(Line v) {
double k = atan2(v.p2.y - v.p1.y, v.p2.x - v.p1.x);
if (sgn(k) < 0)k += pi;
if (sgn(k - pi) == 0)k -= pi;
return k;
}
bool getcross(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4,double &tx,double &ty)//求两直线交点
{
double A1=y2-y1;
double B1=x1-x2;
double C1=cross(x1,y1,x2,y2);
double A2=y4-y3;
double B2=x3-x4;
double C2=cross(x3,y3,x4,y4);
if(fabs(cross(A1,B1,A2,B2))<1e-6)return 0;
tx=cross(C1,B1,C2,B2)/cross(A1,B1,A2,B2);
ty=cross(A1,C1,A2,C2)/cross(A1,B1,A2,B2);
return 1;
}
//点和直线的关系：1为在左侧;2为点在右侧;0为点在直线上
int Point_line_relation(Point p,Line v){
int c = sgn(Cross(p - v.p1, v.p2 - v.p1));
if (c < 0)return 1; //1：p在v的左边
if (c > 0)return 2; //2：p在v的右边
return 0; //0：p在v上
}
//点和线段的关系：0为点p不在线段v上；1为点p在线段v上
bool Point_on_seg(Point p, Line v)
{
return sgn(Cross(p - v.p1, v.p2 - v.p1)) == 0 && sgn(Dot(p - v.p1, p - v.p2)) <= 0;
}
//两直线的关系：0为平行,1为重合,2为相交
int Line_relation(Line v1, Line v2){
if (sgn(Cross(v1.p2 - v1.p1, v2.p2 - v2.p1)) == 0) {
if (Point_line_relation(v1.p1, v2) == 0)return 1; //1：重合
else return 0; //0：平行
}
return 2; //2：相交
}
//点到直线的距离
double Dis_point_line(Point p, Line v) {
return fabs(Cross(p - v.p1, v.p2 - v.p1)) / Distance(v.p1, v.p2);
}
//点在直线上的投影
Point Point_line_proj(Point p, Line v) {
double k = Dot(v.p2 - v.p1, p - v.p1) / Len2(v.p2 - v.p1);
return v.p1 + (v.p2 - v.p1) * k;
}
//点到线段的距离
double Dis_point_seg(Point p, Segment v) {
if (sgn(Dot(p - v.p1, v.p2 - v.p1)) < 0 || sgn(Dot(p - v.p2, v.p1 - v.p2)) < 0)
return min(Distance(p, v.p1), Distance(p, v.p2));//点的投影不在线段上
return Dis_point_line(p, v); //点的投影不在线段上
}
//求两直线ab与cd的交点，在调用前要保证两直线不平行或重合
Point Cross_point(Point a, Point b, Point c, Point d) {
double s1 = Cross(b - a, c - a);
double s2 = Cross(b - a, d - a);
return Point(c.x * s2 - d.x * s1, c.y * s2 - d.y * s1) / (s2 - s1);
}
//两线段是否相交：1为相交，0为不相交
bool Cross_segment(Point a, Point b, Point c, Point d) { //Line1：ab,Line2:cd
double c1 = Cross(b - a, c - a), c2 = Cross(b - a, d - a);
double d1 = Cross(d - c, a - c), d2 = Cross(d - c, b - c);
return sgn(c1) * sgn(c2) < 0 && sgn(d1) * sgn(d2) < 0;
//注意交点是端点的情况不算在内
}
//——————————————平面几何：多边形————————————————————————
struct Polygon
{
int n; //多边形的顶点数
Point p[maxp]; //多边形的点
Line v[maxp]; //多边形的边
};
//判断点和任意多边形的关系：3为点上；2为边上；1为内部；0为外部
int Point_in_polygon(Point pt, Point* p, int n)
{
int i;
for (i = 0; i < n; i++) {
if (p[i] == pt)return 3;
}
for (i = 0; i < n; i++)
{
Line v = Line(p[i],p[(i + 1) % n]);
if (Point_on_seg(pt, v))return 2;
}
int num = 0;
for (int i = 0; i < n; i++)
{
int j = (i + 1)%n;
int c = sgn(Cross(pt - p[j], p[i] - p[j]));
int u = sgn(p[i].y - pt.y);
int v = sgn(p[j].y - pt.y);
if (c > 0 && u < 0 && v >= 0)num++;
if (c < 0 && u >= 0 && v < 0)num--;
}
return num != 0;
}
//多边形面积
double Polygon_area(Point* p, int n) { //从原点开始划分是三角形
double area = 0;
for (int i = 0; i < n; i++)
area += Cross(p[i], p[(i + 1) % n]);
return area / 2; //面积有正负，不能简单地取绝对值
}
double mult(Point a, Point b, Point o) { //计算叉乘 ao 和 bo
return (a.x - o.x) * (b.y - o.y) >= (b.x - o.x) * (a.y - o.y);
}
int Graham(Point p[], int n, Point res[]) { //逆时针排序，构造凸包形状
int top = 1;
sort(p, p + n);
if (n == 0) return 0;
res[0] = p[0];
if (n == 1) return 0;
res[1] = p[1];
if (n == 2) return 0;
res[2] = p[2];
for (int i = 2; i < n; i++) {
while (top && (mult(p[i], res[top], res[top - 1])))
top--;
res[++top] = p[i];
}
int len = top;
res[++top] = p[n - 2];
for (int i = n - 3; i >= 0; i--) {
while (top != len && (mult(p[i], res[top], res[top - 1])))
top--;
res[++top] = p[i];
}
return top;
}
//求多边形的重心
Point Polygon_center(Point* p, int n) {
Point ans(0, 0);
if (Polygon_area(p, n) == 0)return ans;
for (int i = 0; i < n; i++)
ans = ans + (p[i] + p[(i + 1) % n]) * Cross(p[i], p[(i + 1) % n]);
return ans / Polygon_area(p, n) / 6;
}
//Convex_hull()求凸包.凸包顶点放在ch中，返回值是凸包的顶点数
int Convex_hull(Point* p, int n, Point* ch) {
sort(p, p + n); //对点排序：按x从小到大排序，如果x相同，按y排序
n = unique(p, p + n) - p; //去除重复点
int v = 0;
//求下凸包.如果p[i]是右拐弯的，这个点不在凸包上，往回退
for (int i = 0; i < n; i++){
while (v > 1 && sgn(Cross(ch[v - 1] - ch[v - 2], p[i] - ch[v - 2])) <= 0)
v--;
ch[v++] = p[i];
}
int j = v;
//求上凸包
for (int i = n - 2; i >= 0; i--){
while (v > j&& sgn(Cross(ch[v - 1] - ch[v - 2], p[i] - ch[v - 2])) <= 0)
v--;
ch[v++] = p[i];
}
if (n > 1)v--;
return v; //返回值v是凸包的顶点数
}
//——————————————平面几何：圆——————————————
struct Circle {
Point c; //圆心
double r; //半径
Circle(){}
Circle(Point c,double r):c(c),r(r){}
Circle(double x, double y, double _r) { c = Point(x, y); r = _r; }
};
//点和圆的关系：0为点在圆内，1为点在圆上，2为点在圆外
int Point_circle_relation(Point p, Circle C) {
double dst = Distance(p, C.c);
if (sgn(dst - C.r) < 0)return 0; //点在圆内
if (sgn(dst - C.r) == 0)return 1; //圆上
return 2; //圆外
}
//直线和圆的关系：0为直线在圆内，1为直线和圆相切，2为直线在圆外
int Line_circle_relation(Line v, Circle C) {
double dst = Dis_point_line(C.c, v);
if (sgn(dst - C.r) < 0)return 0; //直线在圆内
if (sgn(dst - C.r) == 0)return 1; //直线和圆相切
return 2; //直线在圆外
}
//线段和圆的关系：0为线段在圆内，1为线段和圆相切，2为线段在圆外
int Seg_circle_relation(Segment v, Circle C) {
double dst = Dis_point_seg(C.c, v);
if (sgn(dst - C.r) < 0)return 0; //线段在圆内
if (sgn(dst - C.r) == 0)return 1; //线段和圆相切
return 2; //线段在圆外
}
//直线和圆的交点.pa、pb是交点.返回值是交点的个数
int Line_cross_circle(Line v, Circle C, Point& pa, Point& pb){
if (Line_circle_relation(v, C) == 2)return 0; //无交点
Point q = Point_line_proj(C.c, v); //圆心在直线上的投影点
double d = Dis_point_line(C.c, v); //圆心到直线的距离
double k = sqrt(C.r * C.r - d * d);
if (sgn(k) == 0) { //一个交点，直线和圆相切
pa = q;
pb = q;
return 1;
}
Point n = (v.p2 - v.p1) / Len(v.p2 - v.p1); //单位向量
pa = q + n * k;
pb = q - n * k;
return 2; //两个交点
}
//————————————————三维几何————————————————————————————
//三维：点
struct Point3 {
double x, y, z;
Point3() {}
Point3(double x, double y, double z) :x(x), y(y), z(z){}
Point3 operator + (Point3 B) { return Point3(x + B.x, y + B.y, z + B.z); }
Point3 operator - (Point3 B) { return Point3(x - B.x, y - B.y, z - B.z); }
Point3 operator * (double k) { return Point3(x *k, y *k, z *k); }
Point3 operator / (double k) { return Point3(x / k, y / k, z / k); }
bool operator ==(Point3 B) {
return sgn(x - B.x) == 0 && sgn(y - B.y) == 0 && sgn(z - B.z) == 0;
}
};
typedef Point3 Vector3;
//点积.和二维点积函数同名.c++允许函数同名
double Dot(Vector3 A, Vector3 B) { return A.x * B.x + A.y * B.y + A.z * B.z; }
//叉积
Vector3 Cross(Vector3 A, Vector3 B) {
return Point3(A.y * B.z - A.z * B.y, A.z * B.x - A.x * B.z, A.x * B.y - A.y * B.x);
}
double Len(Vector3 A) { return sqrt(Dot(A, A)); } //向量的长度
double Len2(Vector3 A) { return Dot(A, A); } //向量的长度的平方
double Distance(Point3 A, Point3 B){ //A、B的距离
return sqrt((A.x - B.x) * (A.x - B.x) +
(A.y - B.y) * (A.y - B.y) +
(A.z - B.z) * (A.z - B.z));
}
//A与B的夹角
double Angle(Vector3 A, Vector3 B) { return acos(Dot(A, B) / Len(A) / Len(B)); }
//三维：线
struct Line3 {
Point3 p1, p2;
Line3() {}
Line3(Point3 p1,Point3 p2):p1(p1),p2(p2){}
};
typedef Line3 Segment3; //定义线段，两端点是Point p1,p2
//三维：三角线面积的两倍
double Area2(Point3 A, Point3 B, Point3 C) { return Len(Cross(B - A, C - A)); }
//三维：点到直线的距离
double Dis_point_line(Point3 p, Line3 v) {
return Len(Cross(v.p2 - v.p1, p-v.p1)) / Distance(v.p1, v.p2);
}
//三维：点在直线上
bool Point_line_relation(Point3 p, Line3 v) {
return sgn(Len(Cross(v.p1 - p, v.p2 - p))) == 0
&& sgn(Dot(v.p1 - p, v.p2 - p)) == 0;
}
//三维：点到线段的距离
double Dis_point_seg(Point3 p, Segment3 v) {
if (sgn(Dot(p - v.p1, v.p2 - v.p1)) < 0 || sgn(Dot(p - v.p2, v.p1 - v.p2)) < 0)
return min(Distance(p, v.p1), Distance(p, v.p2));
return Dis_point_line(p, v);
}
//三维：点p在直线上的投影
Point3 Point_line_proj(Point3 p, Line3 v) {
double k = Dot(v.p2 - v.p1, p - v.p1) / Len2(v.p2 - v.p1);
return v.p1 + (v.p2 - v.p1) * k;
}
//三维：平面
struct Plane {
Point3 p1, p2, p3; //平面上的3个点
Plane(){}
Plane(Point3 p1,Point3 p2,Point3 p3):p1(p1),p2(p2),p3(p3){}
};
//平面法向量
Point3 Pvec(Point3 A, Point3 B, Point3 C) { return Cross(B - A, C - A); }
Point3 Pvec(Plane f) { return Cross(f.p2 - f.p1, f.p3 - f.p1); }
//四点共平面
bool Point_on_plane(Point3 A, Point3 B, Point3 C, Point3 D) {
return sgn(Dot(Pvec(A, B, C), D - A)) == 0;
}
//两平面平行
int Parallel(Plane f1, Plane f2) {
return sgn(Dot(Pvec(f1), Pvec(f2)))<eps;
}
//两平面垂直
int Vertical(Plane f1, Plane f2){
return sgn(Dot(Pvec(f1), Pvec(f2))) == 0;
}
//直线与平面的交点p,返回值是交点的个数
int Line_cross_plane(Line3 u, Plane f, Point3& p) {
Point3 v = Pvec(f); //平面的法向量
double x = Dot(v, u.p2 - f.p1);
double y = Dot(v, u.p1 - f.p1);
double d = x - y;
if (sgn(x) == 0 && sgn(y) == 0)return -1; //-1：v在f上
if (sgn(d) == 0)return 0; //0：v与f平行
p = ((u.p1 * x) - (u.p2 * y)) / d; //1：v与f相交
return 1;
}
//四面体有向体积x6
double volume4(Point3 A, Point3 B, Point3 C, Point3 D) {
return Dot(Cross(B - A, C - A), D - A);
}