aoc2023/day5/p2.c

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#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
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) {
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fprintf(stderr, "Cannot open file %s\n", argv[1]);
return -1;
}
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if (getline(&line, &line_buf_length, input) == -1) {
fprintf(stderr, "A file %s ended unexpectedly.", argv[1]);
return -1;
}
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++;
}
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uint64_t *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;
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} 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);
}
uint64_t lowest_loc_n = UINT64_MAX;
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for (size_t i = 0; i < seed_ranges_len; i += 2)
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#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;
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for (size_t j = 0; j < MAPS_LEN; ++j)
for (size_t k = 0; k < map_lengths[j]; ++k)
if (seed >= maps[j][k].src && seed <= maps[j][k].src + maps[j][k].rng) {
seed = maps[j][k].dst + (seed - maps[j][k].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;
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for (size_t m = 1;; m *= 10) {
if (*end>>4 != 0x3)
break;
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num += (*end&0xf) * m;
--end;
}
return num;
}