摘要：
http://oj.leetcode.com/problems/permutations/Given a collection of numbers, return all possible permutations.For example,[1,2,3] have the following permutations:[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].思路：典型的递归问题。生成[2, 3]的全排列[2, 3]和[3, 2]，然后把1加上去生成[1, 2, 3]和[1, 3, 2]。交换1和2的位置，生成[1, 3 阅读全文
