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Subsets.java
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Subsets.java
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package com.leetcode;
import java.util.ArrayList;
import java.util.List;
/**
Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]
Time complexity: O(2^n)
Space complexity: O(n)
// Wrong //O(N×2^N) Space and same O(N×2^N) Time
**/
public class Subsets {
//https://leetcode.com/problems/subsets/
class Solution {
public List<List<Integer>> subsets(int[] nums) {
List<List<Integer>> result = new ArrayList<>();
List<Integer> list = new ArrayList<>();//temp list
backtrack(0,nums,list , result);
return result;
}
public void backtrack(int index , int[] nums, List<Integer> list, List<List<Integer>> result){
result.add(new ArrayList<>(list));//copy a new one
for(int i = index ; i < nums.length ; i++){
list.add(nums[i]);
backtrack(i+1,nums,list,result);
list.remove(list.size()-1);
}
}
}
}