13b.c

   1 #include <stdio.h>
   2
   3 #include <uthash.h>
   4
   5 struct point { int x; int y; };
   6 struct dot { struct point p; UT_hash_handle hh; };
   7
   8 #define pnt(px, py) ((struct point){.x=(px), .y=(py)})
   9
  10 void add_dot(struct dot **grid, struct point p)
  11 {
  12         struct dot *d;
  13         HASH_FIND(hh, *grid, &p, sizeof(struct point), d);
  14         if (!d) {
  15                 d = malloc(sizeof(struct dot));
  16                 d->p = p;
  17                 HASH_ADD(hh, *grid, p, sizeof(struct point), d);
  18         }
  19 }
  20
  21 #define foldp(p, f) ( (f) - ( (p) - (f) ) )
  22
  23 void fold(struct dot **grid, char axis, int num)
  24 {
  25         struct dot *d, *tmp;
  26         HASH_ITER(hh, *grid, d, tmp) {
  27                 struct point p = d->p;
  28                 if (axis == 'x' && p.x >= num) {
  29                         HASH_DEL(*grid, d);
  30                         if (p.x > num)
  31                                 add_dot(grid, pnt(foldp(p.x, num), p.y));
  32                 } else if (axis == 'y' && p.y >= num) {
  33                         HASH_DEL(*grid, d);
  34                         if (p.y > num)
  35                                 add_dot(grid, pnt(p.x, foldp(p.y, num)));
  36                 }
  37         }
  38 }
  39
  40 int main()
  41 {
  42         char *buf = NULL;
  43         size_t len = 0;
  44         struct dot *grid = NULL;
  45
  46         while (getline(&buf, &len, stdin) != -1 && strcmp(buf, "\n") != 0) {
  47                 char *to = strchr(buf, ',');
  48                 *(to++)= '\0';
  49                 add_dot(&grid, pnt(atoi(buf), atoi(to)));
  50         }
  51
  52         int maxx = 0, maxy = 0;
  53         while (getline(&buf, &len, stdin) != -1) {
  54                 char *to = strchr(buf, '=')-1;
  55                 int foldline = atoi(to+2);
  56                 fold (&grid, *to, foldline--);
  57                 if (*to == 'x') maxx = foldline;
  58                 else            maxy = foldline;
  59         }
  60
  61         struct dot *d;
  62         for (int y = 0; y<=maxy; y++) {
  63                 for (int x = 0; x<=maxx; x++) {
  64                         HASH_FIND(hh, grid, &pnt(x, y), sizeof(struct point), d);
  65                         printf("%c", d ? '#' : '.');
  66                 }
  67                 printf("\n");
  68         }
  69 }