Consolidation 3.01 P39799 Circles (2)

#include <iostream>
#include <cmath>
using namespace std;


// Precondition:
struct Point {
    double x, y;};
struct Circle {
    Point center;
    double radius;};
double dist(const Point& a, const Point& b) {
    return sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));}
void move(Point& p1, const Point& p2) {
    p1.x = p1.x + p2.x;
    p1.y = p1.y + p2.y;}
void move(Circle& c, const Point& p) {
    c.center.x = c.center.x + p.x;
    c.center.y = c.center.y + p.y;}
void scale(Circle& c, double sca) {
    c.radius = c.radius * sca;}
bool is_inside(const Point& p, const Circle& c) {
    return dist(c.center,p)<=c.radius;}




void read(Point& p) {
    cin>>p.x>>p.y;}

void read(Circle& c) {
    cin>>c.center.x>>c.center.y>>c.radius;}

int main() {
    Point p,pnext;
    Circle c;
    read(c);
    read(p);
    if (is_inside(p,c)) cout<<"initially inside"<<endl;
    else cout<<"initially outside"<<endl;
    int t;
    cin>>t;
    for (int i=1; i<=t; ++i) {
        bool was_inside = is_inside(p,c);
        cin>>pnext.x>>pnext.y;
        move(p,pnext);
        if (is_inside(p,c) != was_inside) {
            if (is_inside(p,c)) cout<<"in the step "<<i<<" has gone in"<<endl;
            else cout<<"in the step "<<i<<" has gone out"<<endl;
        }
    }
}

// (c) Carlos Sansón (Best pro1 delegate ever for sure) @csansoon