摘要：
Follow up for N-Queens problem. Now, instead outputting board configurations, return the total number of distinct solutions. Example For n=4, there ar 阅读全文
摘要：
The n-queens puzzle is the problem of placing n queens on an n×nchessboard such that no two queens attack each other. Given an integer n, return all d 阅读全文
摘要：
Given a string source and a string target, find the minimum window in source which will contain all the characters in target. Notice If there is no su 阅读全文