p11.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include "intcode.h"

#define WIDTH 120
#define HEIGHT 120
#define WHITE (1)
#define BLACK (0)
#define UNPAINTED_BLACK (-1)

int main(int argc, char **argv) {
    int64_t output[10];
    size_t length;
    
    int64_t *source = load_source_code_from_file(argv[1], &length, 10000);
    int8_t *grid = (int8_t *)calloc(WIDTH*HEIGHT, 1);

    bool pt2 = false;
    bool done = false;
    while (!done) {
        struct program *p = init_program_instance(source, length, output);

        int64_t x = WIDTH*0.5;
        int64_t y = HEIGHT*0.5;
        int64_t dir = 0; // UP

        int64_t min_x = WIDTH;
        int64_t max_x = 0;
        int64_t min_y = HEIGHT;
        int64_t max_y = 0;

        memset(grid, UNPAINTED_BLACK, WIDTH*HEIGHT);

        grid[y*WIDTH + x] = pt2 ? WHITE : UNPAINTED_BLACK;        

        while (true) {
            int64_t input = (grid[y*WIDTH+x] == WHITE) ? WHITE : BLACK;
            p->input = &input;
            p->remaining_inputs = 1;
            if (run_program_instance_until_halted(p)) { break; }
            grid[x+y*WIDTH] = output[0];

            dir = (dir + ((output[1] == 0) ? 3 : 1)) % 4;
            switch (dir) {
                case 0:
                    y--; break;
                case 1:
                    x++; break;
                case 2: 
                    y++; break;
                case 3: 
                    x--; break;
            }
            if (x < 0 || x >= WIDTH || y < 0 || y >= HEIGHT) {
                fprintf(stderr, "out of bounds %lld %lld\n", x, y);
                exit(1);
            }
            if (max_x < x) max_x = x;
            if (min_y > y) min_y = y;
            if (min_x > x) min_x = x;
            if (max_y < y) max_y = y;
        }

        if (!pt2) {
            int count = 0;
            for (size_t i = 0; i < WIDTH*HEIGHT; i++) { if (grid[i] != UNPAINTED_BLACK) count++; }

            printf("Pt 1: %d\n", count);
            pt2 = true;
        } else {
            printf("Pt 2:\n");
            for (int64_t y = min_y; y <= max_y; y++) {
                printf("| ");
                for (int64_t x = min_x; x <= max_x; x++) {
                    printf("%s", (grid[x + y*WIDTH] == WHITE) ? "#" : " ");
                }
                printf(" |\n");
            }
            done = true;
        }

        free_program_instance(p);
    }

    free(grid);
    free(source);
    return 0;
}