[LintCode] Permutations
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/** * @param nums: A list of integers. * @return: A list of permutations. */ public ArrayList<ArrayList<Integer>> permute(ArrayList<Integer> nums) { // write your code here ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>(); if(nums == null || nums.size() == 0) return res; boolean[] visited = new boolean[nums.size()]; ArrayList<Integer> tmp = new ArrayList<Integer>(); dfs(res,visited, tmp, nums); return res; } public void dfs(ArrayList<ArrayList<Integer>> res, boolean[] visited, ArrayList<Integer> tmp, ArrayList<Integer> nums) { if(tmp.size() == nums.size()){ res.add(new ArrayList<Integer>(tmp)); return; } for(int i = 0 ; i < nums.size(); i++) { if(!visited[i]){ visited[i] = true; tmp.add(nums.get(i)); dfs(res, visited,tmp,nums); visited[i] = false; tmp.remove(tmp.size()-1); } } } |
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