八数码问题。九宫格的每一个状态用一个字符串表示，该字符串为将九宫格中的数字从上到下，从左到右的连接起来，空白处用“0”表示。初始状态表示为”123804765”-8 digital issues. Style Box for each state with a string that the string will be the number of five direction pad from top to bottom, left to right to link up the space with " 0" . The initial state is represented as " 123,804,765"