part 1 of day 2 of advent of code 2022 in c

rock_paper_scissors_strategy.c

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

typedef struct {
    /*
     * Each shape is identified by a character.
     * A for rock,
     * B for paper
     * C for scissors
     */
    char id;
    
    /*
     * Each shape allows to obtain a score
     * only for using them
     */
    int score;
    
    char beatable;
    char not_beatable;
} Shape;

int calculate_shape_score(Shape shape) {
    switch (shape.id) {
        case 'A':
            return 1;
        case 'B':
            return 2;
        case 'C':
            return 3;
    }
    
    // In case of unkown shapes
    return 0;
}

Shape get_shape_from_id(char id) {
    Shape shape;
    shape.id = id;
    shape.score = calculate_shape_score(shape);
    
    /*
     * Rock beats scissors,
     * paper beats rock,
     * scissors beats paper
     */
    switch (shape.id) {
        case 'A':
            shape.beatable = 'C';
            shape.not_beatable = 'B';
            break;
        
        case 'B':
            shape.beatable = 'A';
            shape.not_beatable = 'C';
            break;
            
        case 'C':
            shape.beatable = 'B';
            shape.not_beatable = 'A';
            break;
    }
    
    return shape;
}

/*
 * Returns 0 if they're equal,
 * 1 if the first is more important than the second
 * -1 otherwise
 */
int compare_shapes(Shape reference, Shape to_compare) {
    if (reference.id == to_compare.id) {
        return 0;
    }
    
    if (reference.beatable == to_compare.id) {
        return 1;
    }
    
    return -1;
}

/*
 * A struct is used because of the difficulty
 * about returning multidimensional arrays
 */
typedef struct {
    /*
     * The second array has length 4, insted of 3,
     * because one byte is reserved for null byte
     */
    char lines[3][4];
} Lines;

/*
 * Mocks lines read from a text file
 */
Lines read_lines_from_file(char* filename) {
    Lines lines;
    
    strcpy(lines.lines[0], "A B");
    strcpy(lines.lines[1], "C C");
    strcpy(lines.lines[2], "B C");
    
    return lines;
}

int find_score_according_to_strategy_guide(char lines[][4], int number_of_lines) {
        int score_for_shape = 0;
        int score_for_match_outcome = 0;

        for (int i = 0; i < number_of_lines; i++) {
            char* line = lines[i];

            printf("line: %s\n", line);
            Shape shape_selected_by_opponent = get_shape_from_id(line[0]);
            Shape shape_to_respond_with = get_shape_from_id(line[2]);
            
            score_for_shape += shape_to_respond_with.score;

            int match_outcome = compare_shapes(shape_selected_by_opponent, shape_to_respond_with);
            if (match_outcome > 0) {
                score_for_match_outcome += 6;
            } else if (match_outcome == 0) {
                score_for_match_outcome += 3;
            }
            printf("score for shape: %d, score for match: %d\n", score_for_shape, score_for_match_outcome);
            printf("shape opponent: %c, shape to respond: %c\n", shape_selected_by_opponent.id, shape_to_respond_with.id);
        }
    
        return score_for_shape + score_for_match_outcome;
    }

int main(int argc, const char * argv[]) {
    
    Lines lines = read_lines_from_file("filename");
    int score = find_score_according_to_strategy_guide(lines.lines, 3);
    printf("score: %d", score);
    return 0;
}

The file reading code is not actualing working, as the program actually just use some mock data for test.