/* === aoc202406 =======================================================
   Hmmm, I've done something like this already this year... on day 4
   I need rcmap() moved to aocutils ... done; now it's called `linearize2d`
Part Two: brute force? It likely is faster than coming up with an algo
   Let's go: save map, for every available position put in an obstacle,
   loop around until some place is visited 4? times or area is exited
TODO remove linearize2d
===================================================================== */

static bool validpos(unsigned s, int r, int c) {
    if (r < 0) return false;
    if (c < 0) return false;
    if ((unsigned)r >= s - 1) return false;
    if ((unsigned)c >= s - 1) return false;

        accumsum += accum;
    } while ((line = strtok(NULL, "\n")) != NULL);
    printf("The sum of middle update numbers is {%u}.\n", accumsum);
    printf("The sum of middle update numbers for newly ordered updates is {%u}.\n", accumsum2);
}

/* === aoc202404 =======================================================
TODO remove linearize2d
===================================================================== */

static bool masat(char *data, unsigned size, unsigned row, unsigned col, int drow, int dcol) {
    int maxrow = (int)row + 3*drow;
    int maxcol = (int)col + 3*dcol;
    if ((0 <= maxrow) && (maxrow < (int)size) && (0 <= maxcol) && (maxcol < (int)size)) {
        if (data[linearize2d(size+1, (unsigned)((int)row + drow), (unsigned)((int)col + dcol))] != 'M') return false;