用回溯法求马周游问题,马在棋盘上走字步,从马开始的位置开始周游棋盘,遍历全棋盘后回到起点,是否可行,可行的就输出路径,路径并输入尝试过的路径数,跳过的路径数-law with retrospective travel for Ma, Ma on the chessboard characters step away from the start position Ma started to travel around the chessboard, traverse the whole ches