Problem p00625 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define EQ(a, b) (abs((a) - (b)) < EPS)
using namespace std;
typedef long double D;
const D EPS = 1e-8;

D getTime(D dx, D dy, D v, D fpx, D fpy, D fvx, D fvy) {
  D px = fpx - dx, py = fpy - dy;
  D a = fvx * fvx + fvy * fvy - v * v;
  D b = 2 * fvx * px + 2 * fvy * py;
  D c = px * px + py * py;

  if (EQ(a, 0)) {
    if (EQ(b, 0))
      return EQ(c, 0) ? 0 : -1;
    else
      return (-c / b < -EPS) ? -1 : -c / b;
  } else {
    D d = b * b - 4 * a * c;
    if (d < -EPS)
      return -1;
    if (EQ(d, 0))
      return (-b / 2 / a < -EPS) ? -1 : -b / 2 / a;
    D t1 = (-b - sqrt(d)) / 2 / a, t2 = (-b + sqrt(d)) / 2 / a;
    if (t1 < -EPS)
      return (t2 < -EPS) ? -1 : t2;
    return t1;
  }
}

int main() {
  int n, m;
  while (scanf("%d%d", &n, &m), n) {
    vector<D> dx(n), dy(n), v(n);
    rep(i, n) scanf("%Lf%Lf%Lf", &dx[i], &dy[i], &v[i]);

    vector<int> cnt(n, 0);
    rep(i, m) {
      D fpx, fpy, fvx, fvy;
      scanf("%Lf%Lf%Lf%Lf", &fpx, &fpy, &fvx, &fvy);

      D minT = 1e10, minID = -1;
      vector<D> t(n);
      rep(i, n) {
        t[i] = getTime(dx[i], dy[i], v[i], fpx, fpy, fvx, fvy);
        if (t[i] > -EPS && minT > t[i] + EPS) {
          minT = t[i];
          minID = i;
        }
      }

      cnt[minID]++;
      rep(i, n) {
        if (t[i] > -EPS) {
          dx[i] += v[i] * minT;
          dy[i] += v[i] * minT;
        }
      }
    }
    rep(i, n) printf("%d%c", cnt[i], i == n - 1 ? '\n' : ' ');
  }
}

Fixed submission:
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define EQ(a, b) (abs((a) - (b)) < EPS)
using namespace std;
typedef long double D;
const D EPS = 1e-8;

D getTime(D dx, D dy, D v, D fpx, D fpy, D fvx, D fvy) {
  D px = fpx - dx, py = fpy - dy;
  D a = fvx * fvx + fvy * fvy - v * v;
  D b = 2 * fvx * px + 2 * fvy * py;
  D c = px * px + py * py;

  if (EQ(a, 0)) {
    if (EQ(b, 0))
      return EQ(c, 0) ? 0 : -1;
    else
      return (-c / b < -EPS) ? -1 : -c / b;
  } else {
    D d = b * b - 4 * a * c;
    if (d < -EPS)
      return -1;
    if (EQ(d, 0))
      return (-b / 2 / a < -EPS) ? -1 : -b / 2 / a;
    D t1 = (-b - sqrt(d)) / 2 / a, t2 = (-b + sqrt(d)) / 2 / a;
    if (t1 < -EPS)
      return (t2 < -EPS) ? -1 : t2;
    return t1;
  }
}

int main() {
  int n, m;
  while (scanf("%d%d", &n, &m), n) {
    vector<D> dx(n), dy(n), v(n);
    rep(i, n) scanf("%Lf%Lf%Lf", &dx[i], &dy[i], &v[i]);

    vector<int> cnt(n, 0);
    rep(i, m) {
      D fpx, fpy, fvx, fvy;
      scanf("%Lf%Lf%Lf%Lf", &fpx, &fpy, &fvx, &fvy);

      D minT = 1e10, minID = -1;
      vector<D> t(n);
      rep(i, n) {
        t[i] = getTime(dx[i], dy[i], v[i], fpx, fpy, fvx, fvy);
        if (t[i] > -EPS && minT > t[i] + EPS) {
          minT = t[i];
          minID = i;
        }
      }

      cnt[minID]++;
      rep(i, n) {
        if (t[i] > -EPS) {
          D sx = fpx + fvx * t[i] - dx[i], sy = fpy + fvy * t[i] - dy[i];
          D absS = sqrt(sx * sx + sy * sy);
          if (EQ(absS, 0))
            continue;
          sx /= absS;
          sy /= absS;
          dx[i] += sx * v[i] * minT;
          dy[i] += sy * v[i] * minT;
        }
      }
    }
    rep(i, n) printf("%d%c", cnt[i], i == n - 1 ? '\n' : ' ');
  }
}