aoc2023/day1/p2.c

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

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) {
		fprintf(stderr, "Cannot open file %s\n", argv[1]);
		return -1;
	}

    uint64_t calibration_value = 0;

    while (getline(&line, &line_buf_length, input) != -1) {
        uint64_t current_calibration_value = 0;
        int8_t last_digit = 0;

        for (size_t i = 0; i < line_buf_length-1; ++i)
            if (line[i]>>4 == 0x3) {
                if (current_calibration_value == 0)
                    current_calibration_value = (line[i]&0xf) * 10;
                last_digit = line[i]&0xf;
            } else {
                uint8_t digit = 0;

                switch (line[i]) {
                    case 'o': // 1
                        if (i+2 <= line_buf_length)
                            if (line[i+1] == 'n' && line[i+2] == 'e')
                                digit = 1;
                        break;
                    case 't': // 2 3
                        if (i+2 <= line_buf_length)
                            if (line[i+1] == 'w' && line[i+2] == 'o') {
                                digit = 2;
                                break;
                            }
                        if (i+4 <= line_buf_length)
                            if (line[i+1] == 'h' && line[i+2] == 'r' && line[i+3] == 'e' && line[i+4] == 'e')
                                digit = 3;
                        break;
                    case 'f': // 4 5
                        if (i+3 <= line_buf_length)
                            if (line[i+1] == 'o' && line[i+2] == 'u' && line[i+3] == 'r') {
                                digit = 4;
                                break;
                            }
                        if (i+3 <= line_buf_length)
                            if (line[i+1] == 'i' && line[i+2] == 'v' && line[i+3] == 'e')
                                digit = 5;
                        break;
                    case 's': // 6 7
                        if (i+2 <= line_buf_length)
                            if (line[i+1] == 'i' && line[i+2] == 'x') {
                                digit = 6;
                                break;
                            }
                        if (i+4 <= line_buf_length)
                            if (line[i+1] == 'e' && line[i+2] == 'v' && line[i+3] == 'e' && line[i+4] == 'n')
                                digit = 7;
                        break;
                    case 'e': // 8
                        if (i+4 <= line_buf_length)
                            if (line[i+1] == 'i' && line[i+2] == 'g' && line[i+3] == 'h' && line[i+4] == 't')
                                digit = 8;
                        break;
                    case 'n': // 9
                        if (i+3 <= line_buf_length)
                            if (line[i+1] == 'i' && line[i+2] == 'n' && line[i+3] == 'e')
                                digit = 9;
                        break;
                }

                if (digit != 0) {
                    if (current_calibration_value == 0)
                        current_calibration_value = digit * 10;
                    last_digit = digit;
                }
            }

        if (current_calibration_value != 0)
            calibration_value += current_calibration_value + last_digit;

        memset(line, 0, line_buf_length);
    }

    printf("%lu\n", calibration_value);

    return 0;
}