05b.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <stdbool.h>
   4
   5 struct line { enum {horz, vert, diag} d; int x1; int y1; int x2; int y2; };
   6
   7 #define max(x, y) ((x)>(y) ? (x) : (y))
   8 #define min(x, y) ((x)<(y) ? (x) : (y))
   9 #define between(a, a1, a2) ((a) >= min(a1, a2) && (a) <= max(a1, a2))
  10
  11 int parse_lines(struct line lines[], int *maxx, int *maxy)
  12 {
  13         int i = 0;
  14         char buf[1000];
  15         while (fgets(buf, 1000, stdin) != NULL) {
  16                 char *p = &buf[0];
  17                 lines[i].x1 = strtol(p, &p, 10);
  18                 p++;
  19                 lines[i].y1 = strtol(p, &p, 10);
  20                 p+=4;
  21                 lines[i].x2 = strtol(p, &p, 10);
  22                 p++;
  23                 lines[i].y2 = strtol(p, &p, 10);
  24                 if (lines[i].x1 == lines[i].x2)
  25                         lines[i].d = vert;
  26                 else if (lines[i].y1 == lines[i].y2)
  27                         lines[i].d = horz;
  28                 else if (abs(lines[i].y2-lines[i].y1) == abs(lines[i].x2-lines[i].x1))
  29                         lines[i].d = diag;
  30                 else
  31                         continue;
  32                 *maxx = max(*maxx, lines[i].x1);
  33                 *maxx = max(*maxx, lines[i].x2);
  34                 *maxy = max(*maxy, lines[i].y1);
  35                 *maxy = max(*maxy, lines[i].y2);
  36                 i++;
  37         }
  38         return i;
  39 }
  40
  41 bool online(int x, int y, struct line line)
  42 {
  43         int slope;
  44         switch (line.d) {
  45         case horz:
  46                 return y == line.y1 && between(x, line.x1, line.x2);
  47         case vert:
  48                 return x == line.x1 && between(y, line.y1, line.y2);
  49         case diag:
  50                 slope = (line.y2 - line.y1) / (line.x2 - line.x1);
  51                 return y-line.y1 == slope*(x-line.x1)
  52                         && between(y, line.y1, line.y2) && between(x, line.x1, line.x2);
  53         }
  54         return false;
  55 }
  56
  57 int main()
  58 {
  59         struct line lines[1000];
  60         int maxx = 0, maxy = 0;
  61         int nlines = parse_lines(lines, &maxx, &maxy);
  62         int r = 0;
  63         for (int x = 0; x<=maxx; x++) {
  64                 for (int y = 0; y<=maxy; y++) {
  65                         int matches = 0;
  66                         for (int line = 0; line<nlines && matches < 2; line++)
  67                                 if (online(x, y, lines[line]))
  68                                         matches++;
  69                         r = matches >= 2 ? r+1 : r;
  70                 }
  71         }
  72         printf("%d\n", r);
  73 }