摘要：
Given a picture consisting of black and white pixels, and a positive integer N, find the number of black pixels located at some specific row R and col 阅读全文
摘要：
Given a picture consisting of black and white pixels, find the number of black lonely pixels. The picture is represented by a 2D char array consisting 阅读全文
摘要：
The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all 阅读全文