Say yo want a set of points sorted in some counterclockwise order. What is the best (fast, precise, short) way to do it? The `atan2l` function is precise and short but way too slow. I do it like this (tested on [submission:68208420]).↵
↵
~~~~~↵
sort(v.begin(), v.end(), [] (point a, point b) {↵
bool x = a.y >= 0, y = b.y >= 0;↵
return x == y ? a.x * b.y > a.y * b.x : x < y;↵
});↵
~~~~~↵
↵
Just wondering if there's something even shorter. ↵
↵
Update: the above code works only for set of points with no three collinear. The following version (way longer) seems to work for all inputs.↵
↵
~~~~~↵
inline int quad (point p) {↵
if (p.x < 0 and p.y < 0) return 0;↵
if (p.x >= 0 and p.y < 0) return 1;↵
if (p.x >= 0 and p.y >= 0) return 2;↵
if (p.x < 0 and p.y >= 0) return 3;↵
assert(69 == 420);↵
}↵
↵
sort(v.begin(), v.end(), [] (point a, point b) {↵
return quad(a) == quad(b) ? a.x * b.y > a.y * b.x : quad(a) < quad(b);↵
});↵
~~~~~↵
↵
~~~~~↵
sort(v.begin(), v.end(), [] (point a, point b) {↵
bool x = a.y >= 0, y = b.y >= 0;↵
return x == y ? a.x * b.y > a.y * b.x : x < y;↵
});↵
~~~~~↵
↵
Just wondering if there's something even shorter. ↵
↵
Update: the above code works only for set of points with no three collinear. The following version (way longer) seems to work for all inputs.↵
↵
~~~~~↵
inline int quad (point p) {↵
if (p.x < 0 and p.y < 0) return 0;↵
if (p.x >= 0 and p.y < 0) return 1;↵
if (p.x >= 0 and p.y >= 0) return 2;↵
if (p.x < 0 and p.y >= 0) return 3;↵
assert(69 == 420);↵
}↵
↵
sort(v.begin(), v.end(), [] (point a, point b) {↵
return quad(a) == quad(b) ? a.x * b.y > a.y * b.x : quad(a) < quad(b);↵
});↵
~~~~~↵
