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day 17: more code cleaning

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Bruno Raoult
2021-12-27 11:34:09 +01:00
parent 8748eb0f1f
commit 95ef1bc864
1 changed files with 10 additions and 26 deletions
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36
2021/day17/aoc-c.c
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@@ -24,13 +24,6 @@
#include "bits.h" #include "bits.h"
#include "list.h" #include "list.h"
typedef struct vector {
s64 x, y;
} vector_t;
#define TMIN 0
#define TMAX 1
struct target { struct target {
s64 x1, y1; s64 x1, y1;
s64 x2, y2; s64 x2, y2;
@@ -39,7 +32,6 @@ struct target {
struct bounds { struct bounds {
s64 dx_min, dx_max; s64 dx_min, dx_max;
s64 dy_min, dy_max; s64 dy_min, dy_max;
s64 steps_min;
} bounds; } bounds;
inline static int hit(s64 x, s64 y) inline static int hit(s64 x, s64 y)
@@ -57,28 +49,13 @@ static s64 nth(s64 x, s64 n)
return ((2 * x) + -1 * (n - 1)) * n / 2; return ((2 * x) + -1 * (n - 1)) * n / 2;
} }
/* nth_x will stop after initial velocity steps
*/
static s64 nth_x(s64 x0, s64 n) static s64 nth_x(s64 x0, s64 n)
{ {
return n >= x0? nth(x0, x0): nth(x0, n); return n >= x0? nth(x0, x0): nth(x0, n);
} }
/* determine max possible initial dx :
* ( dx )(dx + 1) <= minx * 2
* <=> dx² + dx - minx * 2 <= 0
* solution is x = (-b ± sqrt(b² - 4 * a * c)) / 2 * b, with a = 1, b = 1, c = -2 * minx
* => (-1 ± sqrt(1 + 8 * minx)) / 2 <= 0
*/
static s64 dx_min(s64 xmin)
{
s64 res = (s64) ((-1) + sqrt((double)(1 + 8 * xmin))) / 2;
bounds.steps_min = 1;
bounds.dx_min = res;
//printf("xmin=%ld res=%ld nmin=%ld\n", xmin, res, nmin);
return res;
}
/* The highest solution is the solution of: /* The highest solution is the solution of:
* y1 * (y1 +1) / 2 * y1 * (y1 +1) / 2
* (we can ignore x velocity, as we can reach any target x1 with x velocity * (we can ignore x velocity, as we can reach any target x1 with x velocity
@@ -150,7 +127,14 @@ int main(int ac, char **av)
read_input(); read_input();
dx_min(target.x1); /* determine min possible initial dx :
* ( dx )(dx + 1) <= minx * 2
* <=> dx² + dx - minx * 2 <= 0
* solution is :
* x = (-b ± sqrt(b² - 4 * a * c)) / 2 * b, with a = 1, b = 1, c = -2 * minx
* => (-1 ± sqrt(1 + 8 * minx)) / 2 <= 0
*/
bounds.dx_min = (s64) ((-1) + sqrt((double)(1 + 8 * target.x1))) / 2;
bounds.dx_max = target.x2; bounds.dx_max = target.x2;
bounds.dy_min = target.y1; bounds.dy_min = target.y1;
bounds.dy_max = -target.y1; bounds.dy_max = -target.y1;