LeetCode_46---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].

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 Backtracking

翻译：

Code：

LinkedList<List<Integer>> res = new LinkedList<List<Integer>>();res.add(new ArrayList<Integer>());for (int n : nums) {int size = res.size();for (; size > 0; size--) {List<Integer> r = res.pollFirst();for (int i = 0; i <= r.size(); i++) {List<Integer> t = new ArrayList<Integer>(r);t.add(i, n);res.add(t);}}}return res;