八数码问题：在3×3的方格棋盘上，摆放着1到8这八个数码，有1个方格是空的，其初始状态如图1所示，要求对空格执行空格左移、空格右移、空格上移和空格下移这四个操作使得棋盘从初始状态到目标状态。-Eight digital problem: On the 3 × 3 checkerboard, placed 1-8 eight digital, there is a box is empty, its initial state shown in Figure 1, the requirements for the implementation of the space left blank , spaces to the right, move on down the spaces and spaces of these four operations makes the board　the initial state to a target state.