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].
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public class Solution { public
ArrayList<ArrayList<Integer>> permute(int[] num) { ArrayList<ArrayList<Integer> > result = new
ArrayList<ArrayList<Integer> >(); if(num.length > 0){ ArrayList<Integer> list = new
ArrayList<Integer>(); list.add(num[0]); result.add(list); int
length = 1; for(int
i = 1; i < num.length; ++i){ length *= i; for(int
j = 0; j < length; ++j){ ArrayList<Integer> newList = result.remove(0); for(int
k = 0; k < i + 1; ++k){ ArrayList<Integer> addedList = new
ArrayList<Integer>(); addedList.addAll(newList); addedList.add(k, num[i]); result.add(addedList); } } } } return
result; }} |
原文：http://www.cnblogs.com/averillzheng/p/3542226.html