aoc2023/day5/p2.c
2023-12-06 03:45:36 +04:00

126 lines
3.1 KiB
C

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#define ABS(n) ((n < 0) ? n * -1 : n)
uint64_t parse_number(char *end);
#define MAPS_LEN 7
typedef struct {
uint64_t dst, src, rng;
} map_t;
int main(int argc, char **argv) {
FILE *input;
char *line = NULL;
size_t line_buf_length = 0;
if (argc == 1 || argv[1][0] == '-')
input = stdin;
else if ((input = fopen(argv[1], "r")) == NULL) {
printf("Cannot open file %s\n", argv[1]);
return -1;
}
uint64_t *seed_ranges = NULL;
getline(&line, &line_buf_length, input);
char *colon_pos = strchr(line, ':');
size_t seed_ranges_len = 0;
for (char *space_pos = colon_pos+1; space_pos != NULL; space_pos = strchr(space_pos, ' ')) {
seed_ranges_len++;
space_pos++;
}
seed_ranges = (uint64_t *) calloc(seed_ranges_len, sizeof(uint64_t));
for (size_t i = 0, seeds_pos = (size_t) colon_pos+2;; seeds_pos++) {
while (*(char *)(seeds_pos)>>4 == 0x3) seeds_pos++;
seed_ranges[i++] = parse_number((char *)(seeds_pos-1));
if (*(char *)seeds_pos == '\n')
break;
}
map_t **maps = (map_t **) calloc(MAPS_LEN, sizeof(map_t *));
for (size_t i = 0; i < MAPS_LEN; ++i)
maps[i] = (map_t *) calloc(1, sizeof(map_t));
size_t map_lengths[MAPS_LEN] = {1};
int8_t maps_cur = -1;
while (getline(&line, &line_buf_length, input) != -1) {
if (maps_cur == MAPS_LEN)
break;
if (line[0] == '\n') {
maps_cur++;
continue;
} else if (line[0]>>4 != 0x3) {
continue;
}
map_lengths[maps_cur]++;
maps[maps_cur] = (map_t *) realloc(maps[maps_cur], map_lengths[maps_cur] * sizeof(map_t));
map_t new_range_map = {0};
sscanf(line, "%lu %lu %lu\n", &new_range_map.dst, &new_range_map.src, &new_range_map.rng);
maps[maps_cur][map_lengths[maps_cur]-1] = new_range_map;
memset(line, 0, line_buf_length);
}
maps_cur = 0;
uint64_t lowest_loc_n = UINT64_MAX;
for (size_t i = 0; i < seed_ranges_len; i += 2) {
#pragma omp parallel for shared(lowest_loc_n)
for (uint64_t r = seed_ranges[i]; r < seed_ranges[i] + seed_ranges[i+1]; ++r) {
uint64_t seed = r;
for (size_t j = 0; j < MAPS_LEN; ++j) {
for (size_t n = 0; n < map_lengths[j]; ++n) {
if (seed >= maps[j][n].src && seed <= maps[j][n].src + maps[j][n].rng) {
seed = maps[j][n].dst + (seed - maps[j][n].src);
break;
}
}
}
if (seed < lowest_loc_n)
lowest_loc_n = seed;
}
}
free(seed_ranges);
for (size_t i = 0; i < MAPS_LEN; ++i)
free(maps[i]);
printf("%lu\n", lowest_loc_n);
return 0;
}
uint64_t parse_number(char *end) {
uint64_t num = 0;
for (size_t n = 1;; n *= 10) {
if (*end>>4 != 0x3)
break;
num += (*end&0xf) * n;
--end;
}
return num;
}