aoc2023/day2/p2.c

86 lines
1.9 KiB
C

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
uint64_t parse_number(char *end);
#define SETS_STR_MAX_LEN 200
#define CUBE_RED 0
#define CUBE_GREEN 1
#define CUBE_BLUE 2
int main(int argc, char **argv) {
FILE *input;
char *line = NULL;
size_t line_length = 0;
if (argc == 1 || argv[1][0] == '-')
input = stdin;
else if ((input = fopen(argv[1], "r")) == NULL) {
fprintf(stderr, "Cannot open file %s\n", argv[1]);
return -1;
}
uint64_t power_sum = 0;
while (getline(&line, &line_length, input) != -1) {
char *colon_pos = strchr(line, ':');
char *sets = colon_pos + 2;
char *space_pos = NULL;
int8_t cubes[3] = {0};
while (NULL != (space_pos = strchr(sets, ' '))) {
if (*(space_pos-1) == ',' || *(space_pos-1) == ';') {
sets = space_pos + 1;
continue;
}
uint8_t n = parse_number(space_pos-1);
switch (*(space_pos+1)) {
case 'r':
if (cubes[CUBE_RED] < n)
cubes[CUBE_RED] = n;
break;
case 'g':
if (cubes[CUBE_GREEN] < n)
cubes[CUBE_GREEN] = n;
break;
case 'b':
if (cubes[CUBE_BLUE] < n)
cubes[CUBE_BLUE] = n;
break;
}
sets = space_pos + 1;
}
power_sum += cubes[CUBE_RED] * cubes[CUBE_GREEN] * cubes[CUBE_BLUE];
memset(line, 0, line_length);
}
printf("%lu\n", power_sum);
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;
}