Subsets

Leetcode 78.

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class Solution {
    public List<List<Integer>> subsets(int[] nums) {
       List<Integer> list = new ArrayList<>();
       List<List<Integer>> ans = new ArrayList<>();
       ans.add(list);
       boolean[] visited = new boolean[nums.length];
       for(int i = 1; i <= nums.length;i++){
           backtricking(nums,list,ans,0,i,visited);
       }
      
      return ans;
    }
    public void backtricking(int[] nums,List<Integer> list, List<List<Integer>> ans,int start,int depth,boolean[] visited){
       //recursion stop condition 
       if(list.size() == depth){
           //collect results
           ans.add(new ArrayList<>(list));
        return;
       }

       //for for this loop
       for(int i = start;i < nums.length;i++){
        //process the nodes
          if(visited[i])
            continue;  
        visited[i] = true;
        list.add(nums[i]);
        //recursion 
        backtricking(nums,list,ans,i,depth,visited);
        //undo the previous operation
        visited[i] = false;
        list.remove(list.size() - 1);
       }

    }
}