EXPRESSION ADD OPERATORS | LEETCODE # 282 | PYTHON SOLUTION

In this video we are solving a tricky Facebook and Google interview question: Expression Add Operators (Leetcode # 282).
This question is definitely pretty hard if you haven't seen it before but luckily the solution is quite intuitive and straightforward. You'll be able to understand it quite simply at the end of this video and it's actually quite easy to remember once you've seen it before.
TIMESTAMPS:
00:00 Intro
00:21 Question Prompt
00:43 Basic Example
02:00 Solution Intuition
07:42 Coding
19:36 Time/Space Complexity
22:30 Outro

[@vikramramkumar2087]

Damn.. what a solution!! I was thinking of generating all expressions using recursive backtracking (by inserting operators into num at alternate places), then using the eval() function in python, evaluate the string expression and see if eval(''.join(exp)) == target, append only those exp to res.
Sadly, this approach was giving a TLE 🥲
Great solution btw!

[@45vinitthakkar56]

good explaination!

[@aminebesbes6202]

Great explanation! Thank you!
Could you please prepare a general video to explain how to set-up a DFS parameters and its stop condition (Many LeetCode problems similar to this but always the toughest thing is to identify what parameters are needed for the DFS)

[@aneeshakaushal267]

Thanks. Very well explained :)

[@YT.Nikolay]

Awesome! Thank you, we missed you!

[@manojamrutharaj9071]

Welcome back. Thanks for the cool explanation...

[@drewlee7435]

@Cracking FAANG Thanks for an AMAZING video. It's super concise and easy to understand.
It's been an year but wanted to make a comment on this as I was thinking thru the complexities in the end.
I am not too convinced that the Space Complexity is actually O(N), I think it should be at least O(3^N) similar to Time Complexity.
I say this because I think the space needed doesn't grow linear with additional input, but rather exponentially to the additional input.
Would love to know your thought on this. Thanks

[@user-vt8dd6fj7v]

Nice video. I liked the video. Would like to request “Nested List Weight Sum II”. You solve the first version 4 month ago but not the 2nd one

[@cindysu262]

Awesome!!

[@crackfaang]

Glad you found it helpful! Subscribe if you haven’t already 😃

[@lavanyam3224]

Thanks for the detailed explanation!! I've a query, are we using cur_res as a list instead of a string because strings are immutable and addition of a character to a string takes O(N)?

[@rsKayiira]

Great video could you please do Valid Palindrome III LC 1216.

[@sudhanshukumar3745]

can you explain why in multiplication part of the dfs prev becomes curr_num*prev?

[@lesterdelacruz5088]

because when something like this happends `1-2*3*2` you need that must be the same as `1-(x*y)` at before the `-`. If you step through the code on `1-2*3*2` it will make sense. That's what i did.

[@sudhanshukumar3745]

@@lesterdelacruz5088 hey thanks for the explanation

[@roywastaken]

come back G, shit ain't the same without you

[@crackfaang]

Comeback is planned… sometime later this month 👀

[@roywastaken]

@@crackfaang hell yea!!! prepping for Meta with your videos atm

[@AP-eh6gr]

@@roywastaken same lol. Gotta do those 172 for last 6 mo

[@sauravchandra10]

can anyone help me with the c++ code?

[@anilrai9401]

class Solution {
public:
vector ans;

void rec(int cur_idx, string cur_res, long long cur_sum, long long prev, string &num, int target){
if(cur_idx>=num.size()){
if(cur_sum==target){
ans.push_back(cur_res);
}
return;
}

string cur_str = "";

for(int j=cur_idx;j