Day 17: Add C solution

17/input.txt

@@ -0,0 +1 @@
+target area: x=153..199, y=-114..-75

17/solution.c

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+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+           int                   main(
+        ){int C=0,a             ,b,c,d,X,Y;scanf("%*[^=]=%i..%i, "
+    "y=%i..%i",&a,&b           ,&c,&d);for(X=sqrt(a*2);X<=b;X++){
+ #pragma      omp                 parallel for schedule (static\
+,256)       reduction                                 (+:C)
+             for(Y=                                 c;Y<-c
+             ;Y++){                              int x=0
+             ,y=0,v                             =X,V=Y
+             ;while                            (x<b
+             &&y>c                          &&(x<a
+             ||y>d)                        ){x+=v
+             ;y+=V;                       v=v>0?
+             v-1:0;                      V--;}C
+             +=(x>=                     a&&x<=b
+           &&y>=c&&y                   <=d);}}
+   printf("Silver: %lld\nGo"            "ld: %d"
+  "\n",(llabs(c)-1)*llabs(c)             /2,C);}