Given a list of numbers, return all possible permutations.

 

Example

For nums = [1,2,3], the permutations are:

[  [1,2,3],  [1,3,2],  [2,1,3],  [2,3,1],  [3,1,2],  [3,2,1]]

Challenge

Do it without recursion.

 

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