aoc2022/day09

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

enum {max_size = 2000};

struct cmd {
  char dir;
  int distance;
};

struct location {
  int hx, hy, tx, ty;
};

void updateLoc(struct location* l, struct cmd* c) {
  char dir = c->dir;
  if (dir == 'U') {
    --l->hy;
  } else if (dir == 'D') {
    ++l->hy;
  } else if (dir == 'L') {
    --l->hx;
  } else if (dir == 'R') {
    ++l->hx;
  } else {
    printf("Direction %c not recognised\n", dir);
  }
  printf("head now at %d,%d\n", l->hx, l->hy);
  // tail follows
  if (l->hx - l->tx > 1)
    ++l->tx;
  if (l->tx - l->hx > 1)
    --l->tx;
  if (l->hy - l->ty > 1)
    ++l->ty;
  if (l->ty - l->hy > 1)
    --l->ty;
}

int part1(struct cmd cmds[], int size) {
  printf("in p1\n");
  int grid[max_size][max_size] = {0};
  struct location l;
  l.hx = 1000;
  l.hy = 1000;
  l.tx = 1000;
  l.ty = 1000;
  for (int i = 0; i < size; ++i) {
    printf("command %c %d\n", cmds[i].dir, cmds[i].distance);
    for (int j = 0; j < cmds[i].distance; ++j)
      updateLoc(&l, &cmds[i]);
    printf("location updated\n");
    grid[l.ty][l.tx] = 1;
  }
  int count = 0;
  for (int x = 0; x < max_size; ++x) {
    for (int y = 0; y < max_size; ++y) {
      if (grid[y][x] != 0)
        ++count;
    }
  }
  return count;
}

int main() {
  int i = 0;
  struct cmd list[max_size];
  int ret = 2;
  while (ret == 2) {
    ret = scanf("%c %d\n", &list[i].dir, &list[i].distance);
    if (ret < 2) break;
    ++i;
  }
  printf("read %d intructions\n", i);
  int value = part1(list, i);
  printf("%d\n", value);
  //printf("%d\n", part2(list, i));
}