Improving the efficiency of backtracking

General speaking,backtracking is more efficient than enumeration in quantity,therefore efficiency in problem is very important when inputting a large amount of data.This paper present the classic backtracking as an example,through comparing,explains backtracking efficiency difference under various data structure;when database can be expressed in sparseness matrix,then it can be expressed in 4-way linked list,which improves greatly the efficiency than before.The method is most useful for solving problem by backtracking.