spiral hell.cpp

#include <math.h>

int get_coord(int i, int center_x, int center_y){
    if (i == 0) {
        return (center_x, center_y);
    }
    int base = floor((sqrt(i) - 1) / 2) * 2 + 1; // side of the already filled square
    int cur_i = pow(i - base, 2); // which tile are we on in this layer
    int radius = (base + 1) / 2; // radius of this layer
    int side = 2 * radius + 1;
    int last_col_threshold = pow(base + 2, 2) - side; // at which i do we start filling the last column of this layer
    if (cur_i < side) {
        return (center_x - radius, center_y - radius + cur_i);
    } // first column
    else if (i >= last_col_threshold) { // last column 
        int j = i - last_col_threshold;
        return (center_x + radius, center_y - radius + j);
    }
    else { // the rows
        int j = (cur_i - side) / 2; // x-shift
        int sign; // 1 if top row, -1 if bottom row
        if ((cur_i - side) % 2 == 0) {
            sign = -1;
        } else{
            sign = 1;
        }
        return (center_x - radius + j + 1, center_y + sign * radius);
    }
}