Permutations

Leetcode 46.

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class Solution {
    public List<List<Integer>> permute(int[] nums) {
      List<List<Integer>> ans = new ArrayList<>();
      int numsLength = nums.length;
      if(numsLength == 1){
         List<Integer> list = new ArrayList<Integer>();
         list.add(nums[0]);
         ans.add(list);
         return ans;
      }
      List<Integer> store = new ArrayList<>();
      boolean[] visited = new boolean[numsLength];
      backtricking(ans,store,nums,visited);     
      return ans; 
    }
    public void backtricking(List<List<Integer>> ans, List<Integer> store,int[] nums,boolean[] visited){
       //recursion stop condition
       if(store.size() == nums.length){
           //collect data
           List<Integer> list = new ArrayList<>();
           list.addAll(store);
           ans.add(list);
           return; 
       }
         for(int i = 0; i < nums.length;i++){
             if(visited[i]){
                continue;
             }
             visited[i] = true;
             store.add(nums[i]);
             //recursion 
             backtricking(ans,store,nums,visited);
             //undo previous operation 
             store.remove(store.size() - 1);
            
             visited[i] = false;
         }

    }
}