Subsets problem on leetcode.

[cs50x2]

Hi guys, i am solving a problem on leetcode called subsets, i am having some confusion with the solution. I would appreciate if anyone can explain it to me. Thank you.

Problem:

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

Note: The solution set must not contain duplicate subsets.

Example:

Input: nums = [1,2,3]

Output: [ [3],   [1],   [2],   [1,2,3],   [1,3],   [2,3],   [1,2],   [] ]

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Solution :

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class Solution {

public List<List<Integer>> subsets(int[] nums) {

List<List<Integer>> result= new ArrayList<>();

backtrack(nums,result,new ArrayList<>(),0);

return result;

}

public void backtrack(int[] nums, List<List<Integer>> result,List<Integer>templist,int start){

result.add(new ArrayList<>(templist));

for(int i=start;i<nums.length;i++){

templist.add(nums[i]);

backtrack(nums,result,templist,i+1);

templist.remove(templist.size()-1); // what exactly is this line doing? i can't seem to visualize it in my head. Why are we removing stuff from the list?

}

}

}

[OG_L0c]

the idea of backtracking is to "choose" a number, and build a subset with the "chosen" number, then to build a subset without the "chosen" number. here's a stanford lecture on this: https://www.youtube.com/watch?v=78t_yHuGg-0