ACM

http://zh.wikipedia.org/wiki/ACM%E5%9B%BD%E9%99%85%E5%A4%A7%E5%AD%A6%E7%94%9F%E7%A8%8B%E5%BA%8F%E8%AE%BE%E8%AE%A1%E7%AB%9E%E8%B5%9B

http://stackoverflow.com/questions/2709030/explain-bfs-and-dfs-in-terms-of-backtracking

http://www.cnblogs.com/devymex/archive/2010/08/26/1808716.html