Day 5/C: Solve with a tree

05/solution_2_tree.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#define O 1000
+#define E(a,b,X)if(a==b){X}else
+#define u int
+#define C(x,y)m[x][y]++
+#define P(a,b)a<b?1:-1
+#define L(s,e)u S=P(s,e);for(u c=s;c!=e;c+=S)
+                            int
+                           main(
+                         void){u m
+                       [O][O]={0},x,
+                          X,y,Y,I
+                         =0;while(
+                       fscanf(stdin,
+                    "%i,%i -> %i,%i",&x
+                 ,&y,&X,&Y)==4){E(x,X,L(y,
+                     Y)C(x,c);C(x,Y);)
+                    E(y,Y,L(x,X)C(c,y);
+                  C(X,y);){u h=x,v=y,H=P(
+               x,X),V=P(y,Y);for(;h!=X&&v!=Y
+            ;h+=H,v+=V)C(h,v);C(h,v);};};for(y=
+                0;y<O;y++)for(x=0;x<O;x++)I
+                         +=m[x][y]
+                         >1;printf
+                   ("Answer: %d\n",I);;}