#define _GNU_SOURCE #include #include #include #include #define ISDIGIT(c) (c >= 0x30 && c <= 0x39) inline uint64_t parse_number(const char *line, ssize_t j); 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; } char **engine = NULL; ssize_t engine_line_size = 0; ssize_t engine_lines = 0; while (getline(&line, &line_length, input) != -1) { ssize_t len = strlen(line)-1; if (engine == NULL) { engine = (char **) calloc(len, sizeof(char*)); engine_line_size = len; } engine[engine_lines] = (char*) calloc(len, sizeof(char)); memcpy(engine[engine_lines], line, len); ++engine_lines; memset(line, 0, line_length); } uint64_t part_number = 0; for (ssize_t i = engine_lines-1; i >= 0; --i) for (ssize_t j = engine_line_size-1; j >= 0; --j) { if (engine[i][j] != '*') continue; uint64_t n = 1; int8_t p = 0; if (ISDIGIT(engine[i][j+1])) { n *= parse_number(engine[i], j+1); p++; } if (ISDIGIT(engine[i][j-1])) { n *= parse_number(engine[i], j-1); p++; } if (ISDIGIT(engine[i+1][j])) { n *= parse_number(engine[i+1], j); p++; } else { if (ISDIGIT(engine[i+1][j+1])) { n *= parse_number(engine[i+1], j+1); p++; } if (ISDIGIT(engine[i+1][j-1])) { n *= parse_number(engine[i+1], j-1); p++; } } if (ISDIGIT(engine[i-1][j])) { n *= parse_number(engine[i-1], j); p++; } else { if (ISDIGIT(engine[i-1][j+1])) { n *= parse_number(engine[i-1], j+1); p++; } if (ISDIGIT(engine[i-1][j-1])) { n *= parse_number(engine[i-1], j-1); p++; } } if (p >= 2) part_number += n; } for (ssize_t i = 0; i < engine_lines; ++i) free(engine[i]); free(engine); printf("%lu\n", part_number); return 0; } inline uint64_t parse_number(const char *line, ssize_t j) { uint64_t n = 0; uint64_t multiplier = 1; while (ISDIGIT(line[j+1])) j++; while (ISDIGIT(line[j])) { n += (line[j]&0xf) * multiplier; multiplier *= 10; j--; } return n; }