摘要：
Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique p 阅读全文
摘要：
Given a collection of distinct numbers, return all possible permutations. For example, [1,2,3] have the following permutations: [ [1,2,3], [1,3,2], [2 阅读全文