AOC-2021/day-10-part1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LINE_SIZE 4000
#define STACK_SIZE 5000

typedef enum token_type {
    PAREN_OPEN, PAREN_CLOSE,
    BRACKET_OPEN, BRACKET_CLOSE,
    BRACE_OPEN, BRACE_CLOSE,
    AB_OPEN, AB_CLOSE, // AB == angle brackets
    END
} TokenType;

const char *t2s(TokenType t) {
    switch(t) {
        case PAREN_OPEN: return "PAREN_OPEN";
        case PAREN_CLOSE: return "PAREN_CLOSE";
        case BRACKET_OPEN: return "BRACKET_OPEN";
        case BRACKET_CLOSE: return "BRACKET_CLOSE";
        case BRACE_OPEN: return "BRACE_OPEN";
        case BRACE_CLOSE: return "BRACE_CLOSE";
        case AB_OPEN: return "AB_OPEN";
        case AB_CLOSE: return "AB_CLOSE";
        case END: return "END";
        default:
            break;
    }
    return "UNKNOWN";
}

typedef struct line {
    TokenType types[LINE_SIZE]; // assuming longest line is less than LINE_SIZE characters
    int line;
} Line;

void dumpLine(Line *line) {
    printf("line %d\n", line->line);
    for(int i = 0; i < LINE_SIZE && line->types[i] != END; i++) {
        printf("| %s ", t2s(line->types[i]));
    }
    printf("|\n");
}

int linelen(Line *l) {
    int size;
    for(size = 0; l->types[size] != END; size++);
    return size;
}

void scanLine(char *buffer, Line *line, int linenum) {
    for(int i = 0; i < (int)strlen(buffer); i++) {
        switch(buffer[i]) {
            case '(': line->types[i] = PAREN_OPEN; break;
            case ')': line->types[i] = PAREN_CLOSE; break;
            case '[': line->types[i] = BRACKET_OPEN; break;
            case ']': line->types[i] = BRACKET_CLOSE; break;
            case '{': line->types[i] = BRACE_OPEN; break;
            case '}': line->types[i] = BRACE_CLOSE; break;
            case '<': line->types[i] = AB_OPEN; break;
            case '>': line->types[i] = AB_CLOSE; break;
            case '\n': line->types[i] = END; break;
            default:
                fprintf(stderr, "ERROR: unknown character '%c' in line %d!\n", buffer[i], linenum);
                exit(1);
        }
    }
    line->line = linenum;
}

Line *readInput(const char *filename, size_t *size) {
    FILE *f = fopen(filename, "r");
    if(f == NULL) return NULL;

    fseek(f, 0, SEEK_END);
    size_t fsize = ftell(f);
    rewind(f);

    Line *lines = malloc(sizeof(*lines) * fsize);
    int idx = 0;
    char buffer[LINE_SIZE] = {0};
    while(fgets(buffer, LINE_SIZE, f) != NULL) {
        scanLine(buffer, &lines[idx], idx);
        idx++;
        (*size)++;
    }


    fclose(f);
    return lines;
}

TokenType stack[STACK_SIZE] = {-1};
int sp = -1;
void push(TokenType v) {
    if(sp + 1 == STACK_SIZE) {
        fputs("ERROR: stack is full!\n", stderr);
        exit(1);
    }
    stack[++sp] = v;
}
TokenType pop() { return stack[sp--]; }

void check(Line *l, int *score) {
    for(int i = 0; i < linelen(l); i++) {
        switch(l->types[i]) {
            case PAREN_OPEN: push(PAREN_OPEN); break;
            case PAREN_CLOSE:
                if(pop() != PAREN_OPEN) {
                    *score += 3;
                    goto end;
                }
                break;
            case BRACKET_OPEN: push(BRACKET_OPEN); break;
            case BRACKET_CLOSE:
                if(pop() != BRACKET_OPEN) {
                    *score += 57;
                    goto end;
                }
                break;
            case BRACE_OPEN: push(BRACE_OPEN); break;
            case BRACE_CLOSE:
                if(pop() != BRACE_OPEN) {
                    *score += 1197;
                    goto end;
                }
                break;
            case AB_OPEN: push(AB_OPEN); break;
            case AB_CLOSE:
                if(pop() != AB_OPEN) {
                    *score += 25137;
                    goto end;
                }
                break;
        }
    }
end:
    return;
}

int main(void) {
    size_t size = 0;
    Line *input = readInput("input.txt", &size);
    int score = 0;

    for(int i = 0; i < (int)size; i++) {
        check(&input[i], &score);
    }

    free(input);

    printf("score: %d\n", score);
    return 0;
}