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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
enum dir { N, E, S, W };
// I <3 recursion
enum dir rotate(enum dir dir, int cnt, int r)
{
if (!cnt)
return dir;
if (r) { // right
if (dir == W)
dir = N;
else
dir++;
} else { // left
if (dir == N)
dir = W;
else
dir--;
}
return rotate(dir, cnt - 1, r);
}
// Quite inefficient but I like this approach.
int *rotate_wp(int dirs[], int cnt, int r)
{
if (!cnt)
return dirs;
if (r) {
int tmp = dirs[W];
dirs[W] = dirs[S];
dirs[S] = dirs[E];
dirs[E] = dirs[N];
dirs[N] = tmp;
} else {
int tmp = dirs[N];
dirs[N] = dirs[E];
dirs[E] = dirs[S];
dirs[S] = dirs[W];
dirs[W] = tmp;
}
return rotate_wp(dirs, cnt - 1, r);
}
int part_one(FILE *fp)
{
char *line = NULL;
size_t len = 0;
int coords[4] = { 0 };
enum dir cur = E;
while (getline(&line, &len, fp) != -1) {
char dir;
int cnt;
sscanf(line, "%c%d\n", &dir, &cnt);
switch (dir) {
case 'N':
coords[N] += cnt;
break;
case 'E':
coords[E] += cnt;
break;
case 'S':
coords[S] += cnt;
break;
case 'W':
coords[W] += cnt;
break;
case 'L':
cur = rotate(cur, cnt / 90, 0);
break;
case 'R':
cur = rotate(cur, cnt / 90, 1);
break;
case 'F':
coords[cur] += cnt;
break;
default:
break;
}
}
return abs((coords[E] - coords[W]) + (coords[S] - coords[N]));
}
int part_two(FILE *fp)
{
char *line = NULL;
size_t len = 0;
int wp[4] = { 1, 10, 0, 0 };
int coords[4] = { 0 };
enum dir cur = E;
while (getline(&line, &len, fp) != -1) {
char dir;
int cnt;
sscanf(line, "%c%d\n", &dir, &cnt);
switch (dir) {
case 'N':
wp[N] += cnt;
break;
case 'E':
wp[E] += cnt;
break;
case 'S':
wp[S] += cnt;
break;
case 'W':
wp[W] += cnt;
break;
case 'L':
rotate_wp(wp, cnt / 90, 0);
break;
case 'R':
rotate_wp(wp, cnt / 90, 1);
break;
case 'F':
coords[N] += cnt * wp[N];
coords[E] += cnt * wp[E];
coords[S] += cnt * wp[S];
coords[W] += cnt * wp[W];
break;
default:
break;
}
}
return abs((coords[E] - coords[W])) + abs((coords[S] - coords[N]));
}
int main(int argc, char *argv[])
{
FILE *fp = fopen("input", "r");
if (!fp)
exit(EXIT_FAILURE);
clock_t tic = clock();
printf("%d\n", part_one(fp));
rewind(fp);
printf("%d\n", part_two(fp));
clock_t toc = clock();
printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
fclose(fp);
return 0;
}
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