Subsets

subsets.js

/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var subsets = function(nums) {
    let temp = [];
    let res = [];

    function rec(nums, i = 0) {
        if(i === nums.length ) return res.push([...temp]);
        temp.push(nums[i]);
        rec(nums, i + 1);
        temp.pop();
        rec(nums, i + 1);
    }

    rec(nums, 0);

    return res;
};

// make a recursive function that run from 0 to length of nums
// at each num we have a choice to choose that num or not choose it
// if we choose if, we push it in temp array and move on to the next num
// if we dont choose it, we remove it from the temp array and carry on to the next element
// keep doing this till we hit the last element
// push whatever we have in temp into res array (Base case)

// Time: O(2^n)
// Space: O(n)