摘要：
Problem:Given a collection of integers that might contain duplicates,nums, return all possible subsets.Note:Elements in a subset must be in non-descen... 阅读全文
摘要：
Problem:Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2]have the following uni... 阅读全文
摘要：
Problem:Find all possible combinations ofknumbers that add up to a numbern, given that only numbers from 1 to 9 can be used and each combination shoul... 阅读全文