Description

//
// There is a red particle and a green particle in a box.
// The box has (x,y) coordinates 0 <= x <= 10, 0 <= y <= 10.
// The user enters initial (x,y) coordinates for the two
// particles. The velocity of a particle is given as
// an (x,y) pair, where each coordinate is the distance
// the particle moves in that direction, in one cycle.
// Initially, the red particle starts with velocity (1,1),
// and the green particle starts with velocity (-1,-1).
//
// The program simulates the movement of the two particles.
// When a particle reaches a wall, it will bounce
// off the wall. When the two particles are too close together,
// they will collide and the simulation will end.
//
// Each particle is represented by an array of four ints.
// Element 0 and 1 are the (x,y) coordinates of the particle.
// Element 2 and 3 are the (x,y) velocity components of the
// particle.
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
void updatePoint(int *);
int findDistance(int, int, int, int);
int main()
{
int redData[4], greenData[4];
int i,cycle=0, dist;
// set initial conditions
redData[2] = 1;
redData[3] = 1;
greenData[2] = -1;
greenData[3] = -1;
cout << "Enter x-coordinate for red particle (0 to 10):";
cin >> redData[0];
cout << "Enter y-coordinate for red particle (0 to 10):";
cin >> redData[1];
cout << "Enter x-coordinate for green particle (0 to 10):";
cin >> greenData[0];
cout << "Enter y-coordinate for green particle (0 to 10):";
cin >> greenData[1];
do {
// display state of particles
cout << "cycle " << cycle << endl;
cout << "red particle (x,y,xVel,yVel): " << redData[0] << " " << redData[1]
<< " " << redData[2] << " " << redData[3] << endl;
cout << "green particle (x,y,xVel,yVel): " << greenData[0] << " "
<< greenData[1] << " " << greenData[2] << " " << greenData[3]
<< endl << endl;
// update particle positions and velocities
updatePoint(redData);
updatePoint(greenData);
// check distance between particles
dist = findDistance(redData[0], redData[1], greenData[0], greenData[1]);
cycle++;
} while ((dist > 2) && (cycle < 10));
if (dist <= 2) {
cout << "Collison: oops, end of simulation!\n";
cout << "red particle (x,y,xVel,yVel): " << redData[0] << " " << redData[1]
<< " " << redData[2] << " " << redData[3] << endl;
cout << "green particle (x,y,xVel,yVel): " << greenData[0] << " "
<< greenData[1] << " " << greenData[2] << " " << greenData[3]
<< endl << endl;
}
}
// update position and velocity of particle
// arg is array of data for particle
void updatePoint(int *arg)
{
int distance;
distance = findDistance(arg[0],arg[1],0,-1);
if ((distance < 1) && (arg[2] < 0))
arg[2] = - arg[2];
distance = findDistance(arg[0],arg[1],10,-1);
if ((distance < 1) && (arg[2] > 0))
arg[2] = - arg[2];
distance = findDistance(arg[0],arg[1],-1,0);
if ((distance < 1) && (arg[3] < 0))
arg[3] = - arg[3];
distance = findDistance(arg[0],arg[1],-1,10);
if ((distance < 1) && (arg[3] > 0))
arg[3] = - arg[3];
arg[0] = arg[0] + arg[2];
arg[1] = arg[1] + arg[3];
return;
}
// find Manhattan distance between two particles, or between
// a particle and a wall
// (arg0,arg1) are the (x,y) coordinates for first particle/wall
// (arg2,arg3) are the (x,y) coordinates for second particle/wall
int findDistance(int arg0, int arg1, int arg2, int arg3)
{
int distX, distY;
distX = arg0 - arg2;
if (distX < 0)
distX = - distX;
distY = arg1 - arg3;
if (distY < 0)
distY = - distY;
if ((arg0 < 0) || (arg2 < 0))
return distY;
else if ((arg1 < 0) || (arg3 < 0))
return distX;
else
return distX + distY;