LeetCode 78. Subsets (Java)

LeetCode 78. Subsets (Java)

Description

https://leetcode.com/problems/subsets/description/

Given a set of distinct integers, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,3], a solution is:

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

Explanation

The problem is a typical depth first search coding problem.

We can have a recursion function to add visited subsets to the final results. Remember to make a deep copy when we need to add subset to the results.

Video Tutorial

Java Solution

class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> results = new ArrayList<>();
        
        if (nums == null || nums.length == 0) {
            return results;
        }
        
        Arrays.sort(nums);
        
        List<Integer> subset = new ArrayList<>();
        toFindAllSubsets(nums, results, subset, 0);                
        
        return results;
    }
    
    private void toFindAllSubsets(int[] nums, List<List<Integer>> results, List<Integer> subset, int startIndex) {
        results.add(new ArrayList<>(subset));
        
        for (int i = startIndex; i < nums.length; i++) {
            subset.add(nums[i]);
            toFindAllSubsets(nums, results, subset, i + 1);
            subset.remove(subset.size() - 1);            
        }        
    }
}

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