① if ((choice == 2 && player == 2) || (choice == 3 && player == 1))
② if (0 <= xpos && xpos < XMAX && num[xpos] < YMAX)
③ board[xpos][num[xpos]++] = player;

④ for (x = 0, y = ypos, n = 0; x < XMAX; x++)
⑤ for (x = xpos, y = 0, n = 0; y <= ypos; y++)
⑥ for (x = 0, y = ypos - xpos, n = 0; y < YMAX; x++, y++)
⑦ for (x = xpos - ypos, y = 0, n = 0; x < XMAX; x++, y++)
⑧ for (x = 0, y = xpos + ypos, n = 0; y >= 0; x++, y--)
⑨ for (x = xpos + ypos - YMAX + 1, y = YMAX - 1, n = 0; x < XMAX; x++, y--)
の各条件文内でどーゆー計算、アルゴリズムがされてるか教えてくださる人いますか？？