Question Definition
Given a collection of distinct 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],
[3,2,1]
]
Java Solution
public List<List<Integer>> permute(int[] nums) {
boolean[] visited = new boolean[nums.length];
List<Integer> cur = new LinkedList<>();
List<List<Integer>> result = new LinkedList<>();
helper(nums, visited, cur, result);
return result;
}
private void helper(int[] nums, boolean[] visited, List<Integer> cur, List<List<Integer>> result){
if(cur.size() == nums.length){
result.add(new LinkedList<>(cur));
return;
}
for(int i = 0; i < nums.length; i++) {
if(!visited[i]){
visited[i] = true;
cur.add(nums[i]);
helper(nums, visited, cur, result);
cur.remove(cur.size() - 1);
visited[i] = false;
}
}
}
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