1 files changed, 82 insertions, 0 deletions
diff --git a/2017/22.c b/2017/22.c
new file mode 100644
index 0000000..ff73c8c
--- /dev/null
+++ b/2017/22.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+static void printchart(int size,char *chart,int curx,int cury){
+	for(int i=0;i<size;i++){
+		for(int j=0;j<size;j++){
+			if(cury==i&&curx==j)putchar('[');
+			else if(cury==i&&curx==j-1)putchar(']');
+			else putchar(' ');
+			putchar(".W#F"[(int)chart[size*i+j]]);
+		}
+		if(cury==i&&curx==size-1)putchar(']');
+		putchar('\n');
+	}
+}
+
+static int embiggen(int *sizep,char **chartp){
+	int size=*sizep;
+	char *chart=*chartp;
+
+	int newsize=2*size-1,d=(size-1)/2;
+	char *newchart=calloc(newsize*newsize,1);
+	for(int i=0;i<size;i++){
+		memcpy(newchart+newsize*(i+d)+d,chart+size*i,size);
+	}
+	free(chart);
+	*sizep=newsize;
+	*chartp=newchart;
+	return d;
+}
+
+static int virus1[4][2]={{2,3}, {0,0}, {0,1}, {0,0}};
+static int virus2[4][2]={{1,3}, {2,0}, {3,1}, {0,2}};
+
+static int simulate(int size,const char *origchart,int virus[4][2],int nsteps){
+	char *chart=malloc(size*size);
+	memcpy(chart,origchart,size*size);
+	int curx=size/2,cury=size/2,dir=0;
+	int ninf=0;
+	for(int iter=0;iter<nsteps;iter++){
+		if(curx<0||cury<0||curx>=size||cury>=size){
+			int d=embiggen(&size,&chart);
+			curx+=d; cury+=d;
+		}
+
+		int v=chart[size*cury+curx];
+		dir=(dir+virus[v][1])%4;
+		v=virus[v][0];
+		chart[size*cury+curx]=v;
+		if(v==2)ninf++;
+
+		switch(dir){
+			case 0: cury--; break;
+			case 1: curx++; break;
+			case 2: cury++; break;
+			case 3: curx--; break;
+		}
+	}
+	return ninf;
+}
+
+int main(void){
+	freopen("22.in","r",stdin);
+	char *line=NULL;
+	size_t linecap=0;
+	int size=getline(&line,&linecap,stdin)-1;
+
+	char *chart=malloc(size*size);
+	for(int i=0;i<size;i++)chart[i]=line[i]=='#'?2:0;
+	for(int i=1;i<size;i++){
+		getline(&line,&linecap,stdin);
+		for(int j=0;j<size;j++)chart[size*i+j]=line[j]=='#'?2:0;
+	}
+
+	int curx=size/2,cury=size/2;
+	printchart(size,chart,curx,cury);
+
+	printf("%d\n",simulate(size,chart,virus1,10000));
+	printf("%d\n",simulate(size,chart,virus2,10000000));
+}