94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <stdcountof.h>
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char input[] = {
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#embed "day1_input"
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};
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char test[] = {
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#embed "day1_test"
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};
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unsigned grabnum(const char *s, const char **end) {
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unsigned r = 0;
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for (; *s >= '0' && *s <= '9'; s++)
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r = r * 10 + (*s - '0');
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*end = s;
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return r;
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}
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unsigned long do_part1(size_t src_len, const char src[src_len]) {
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const char *s = src;
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unsigned long count = 0;
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unsigned long pos = 1'000'000'000'050;
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while (s < &src[src_len]) {
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const char *ns = s + 1;
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unsigned r = grabnum(ns, &ns);
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if (*s == 'L') {
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pos -= r;
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} else {
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pos += r;
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}
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count += pos % 100 == 0;
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s = ns + 1;
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}
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return count;
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}
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unsigned do_part2(size_t src_len, const char src[src_len]) {
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const char *s = src, *ns = s + 1;
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unsigned count = 0;
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unsigned pos = 50;
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for (;s < &src[src_len]; s = ns + 1, ns = s + 1) {
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unsigned r = grabnum(ns, &ns);
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if (*s == 'L') {
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if (pos == 0) pos = 100;
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unsigned to_zero = pos;
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if (r < to_zero) {
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pos -= r;
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} else {
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unsigned over = r - to_zero;
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unsigned rots = over / 100;
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unsigned adjust = over % 100;
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count += 1 + rots;
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pos = (100 - adjust) % 100;
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}
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} else {
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unsigned to_zero = 100 - pos;
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if (r < to_zero) {
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pos += r;
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} else {
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unsigned over = r - to_zero;
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unsigned rots = over / 100;
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unsigned adjust = over % 100;
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count += 1 + rots;
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pos = adjust;
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}
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}
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}
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return count;
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}
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int main() {
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printf("PART 1 TEST: ");
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if (unsigned long v = do_part1(countof(test), test); v != 3) {
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printf("FAILED (got %lu, expected 3)\n", v);
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} else {
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printf("PASSED\n");
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}
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printf("PART 1 RESULT: %lu\n",
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do_part1(countof(input), input));
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printf("PART 2 TEST: ");
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if (unsigned v = do_part2(countof(test), test); v != 6) {
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printf("FAILED (got %u, expected 6)\n", v);
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} else {
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printf("PASSED\n");
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}
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printf("PART 2 RESULT: %u\n",
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do_part2(countof(input), input));
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}
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