Exercise 2.1: Eight Queens modify the program in question, it is not running in output after the first solution.
Solution: To make it a solution to return, must first obtain a solution, then back or stop running
Exercise 2.2: Another way to solve the eight queens problem is that all permutations between Mr. Cheng 1-8, followed by traversing these arrangements, check each arrangement is a valid solution of the problem of the eight queens Use this method to modify. program, and to compare the performance difference between the old program and the new program.