46. Permutations
https://leetcode.com/problems/permutations/
Related problems
47-permutations-ii
78-subsets
90-subsets-ii
39-combination-sum
---
Given a collection of distinct integers, return all possible permutations.
Example:
Input: [1,2,3] Output: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ]---
Related problems
47-permutations-ii
78-subsets
90-subsets-ii
39-combination-sum
---
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| class Solution { | |
| public List<List<Integer>> permute(int[] nums) { | |
| List<List<Integer>> ans = new ArrayList<List<Integer>>(); | |
| // faster lookup over set contains or list contains | |
| boolean[] visited = new boolean[nums.length]; | |
| dfs(nums, visited, new ArrayList<Integer>(), ans); | |
| return ans; | |
| } | |
| private void dfs(int[] nums, boolean[] visited, List<Integer> prefix, List<List<Integer>> ans) { | |
| if (prefix.size() == nums.length) { | |
| ans.add(new ArrayList<Integer>(prefix)); | |
| return; | |
| } | |
| for (int i = 0; i < nums.length; i++) { | |
| if (visited[i]) { | |
| continue; | |
| } | |
| prefix.add(nums[i]); | |
| visited[i] = true; | |
| dfs(nums, visited, prefix, ans); | |
| // Backtrack | |
| prefix.remove(prefix.size() - 1); | |
| visited[i] = false; | |
| } | |
| } | |
| } |
