回溯.rar是一种系统地搜索问题的解的方法。回溯算法的基本思想是：从一条路往前走，能进则进，不能进则退回来，换一条路再试。-Back. Rar is a systematic search of the solution method. The basic idea of backtracking algorithm is: from one way forward, can be entered into, can not enter the return to, try another ro