I’m new here and have been trying to solve my first problem: TELEPORT. I have submitted a bunch of solutions (in c++) which all give the wrong answer about half of the time (and the other half correct). I can’t figure out what goes wrong in some of the cases. I would be very thankful if someone could help me out. I know the memory usage is not optimal, but this does not seem to be the problem.

```
#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
using namespace std;
class Teleport
{
public:
Teleport(unsigned long int a, unsigned long int b) : x(a), y(b){}
unsigned long int get_x(){return this->x;}
unsigned long int get_y(){return this->y;};
static void setR(unsigned long int c){R=c;};
static unsigned long int R;
protected:
private:
unsigned long int x, y;
};
unsigned long int Teleport::R = 0;
void add_teleport(vector<Teleport> &teleports, unsigned long int i, unsigned long int j);
bool check_teleport(vector<Teleport> &teleports, unsigned long int i, unsigned long int j);
int main()
{
vector<Teleport> teleports;
unsigned long int Q, r, i, j;
char ch;
cin >> Q >> r;
Teleport::setR(r);
for(unsigned long int loop=0; loop<Q;loop++)
{
cin >> ch >> i >> j;
if(ch == '+') // add a teleport
add_teleport(teleports, i, j);
else if(ch == '?') // check if you can reach teleport j from teleport i
{
add_teleport(teleports,0,0); // not optimal memory usage
if(check_teleport(teleports,i,j)) //print DA if it's possible, otherwise NET
puts("DA");
else puts("NET");
}
}
return 0;
}
//adds a teleport att position (i,j)
void add_teleport(vector<Teleport> &teleports, unsigned long int i, unsigned long int j) {
Teleport tp(i,j);
teleports.push_back(tp);
}
//checks if it is possible to reach teleport j from teleport i
bool check_teleport(vector<Teleport> &teleports, unsigned long int i, unsigned long int j) {
unsigned long int x_1 = teleports[i-1].get_x();
unsigned long int y_1 = teleports[i-1].get_y();
unsigned long int x_2 = teleports[j-1].get_x();
unsigned long int y_2 = teleports[j-1].get_y();
double mid_x = (double)x_1/2. + (double)x_2/2.;
double mid_y = (double)y_1/2. + (double)y_2/2.;
return (fabs(x_1-mid_x)+fabs(y_1-mid_y) <= Teleport::R) && (fabs(x_2-mid_x)+fabs(y_2-mid_y) <= Teleport::R);
}
```