Decode Ways (LeetCode 91) | Full Solution with visuals | Recursion to Dynamic Programming

[@lamebert]

This is insane, i wasnt able to understand the neetcode solution, but i am able to understand this! Thanks

[@thisissheraf2633]

NeetCode is also good, however, this is a simplified version with a dp array, and coming up with this solution in an unseen problem is very difficult. Please develop the understanding with recursion + memoization as explained by neetcode, it will be very helpful long term.

[@LinhHoang-ml1qo]

​@@thisissheraf2633 Agree!

[@gamasterprochannel856]

This man is genius

[@chandan07talreja]

Thanks for detailed explanation Nikhil. Really appreciate it.

[@Md_sadiq_Md]

Pushing the algorithm

[@yomamasofat413]

bro who would be able to come up with this solution if he has never seen it before in an interview? Crazy man

[@nivedhitha704]

very very perfect solution....i love this explanation...u made it very easy to understand for beginners...thank you so much sir

[@floatingfortress721]

Thank you very much! You were able to simplify the problem for me and now I actually understand it

[@rudreshcm4172]

Hey nikhil, first of all thanks for your top notch leetcode video solutions. Can you please make one video that should provide roadmap specific to your uploaded playlists/videos. This really make difference and increase watch count.

[@nikoo28]

I have created some playlists, but yes...can define a better roadmap too. Will work on it. Thanks. :)

[@Satya-g5t]

always good explanation, consistent and patient with no hurry, cool. 😃

[@banadipmudi3186]

Thanks brother, amazing explanation

[@KoundinyaKoorapati-o8v]

Nikhil you make things so simple. I really wish you conducted some course in DSA. Thank You.

[@satyadharkumarchintagunta3793]

Thanks bro! Neat and clear explanation.

[@sanjith3075]

this video cleared my doubts , tqsm

[@shubhamsharma8820]

very well explained

[@akshitjain2906]

legend

[@prashanthshetty8337]

Thank you very much for the detailed explanation. instead of dp[], we could use 2 place holders to keep track of previous sum right? all we care is i-1 and i-2 can be tracked as prev1 and prev2.

[@nikoo28]

That's a great idea! Will save you space.

[@Techgether]

"dp[0] = 1 because there is 1 way to decode it, which is not doing anything"... this is not doing anything but still counted as 1 way????? kinda contradict when its only counted as 1 if there is something to decode, which is why when digit is 0, there is 0 way to decode.. but when digit is empty which is at 0 index, now its counted as 1.. this is hard to understand..

[@benmyths]

also in counting stair problem there was a base condition where when you are standing on 0th stairs, theres only 1 way to reach it that is by doing nothing. so dp[0] = 1 😂😂😂 man its so confusing

[@tamils12345]

class Solution { public: int numDecodings(string s) { vector dp(s.length() + 1); dp[0] = 1; dp[1] = (s.at(0) == '0')?0:1; for(int i = 2; i= 1) { dp[i] += dp[i-1]; } if (double_digit >= 10 && double_digit

[@jst8922]

The issue stems from how you're extracting single and double-digit numbers using stoi and substr. Here's a breakdown of the problem and the solution: Problem: Incorrect Substring Extraction: The substr(i-1, i) in stoi(s.substr(i-1, i)) doesn't extract a single digit. Instead, it extracts a substring from index i-1 up to (but not including) index i. This means you're always getting a two-character substring (except for the last iteration). Unnecessary stoi: You don't need stoi to check if a single digit is between 1 and 9. A simple character comparison is more efficient. tested & working on lc class Solution { public: int numDecodings(string s) { int n = s.length(); vector dp(n + 1); dp[0] = 1; // Empty substring has one way to decode dp[1] = (s[0] == '0') ? 0 : 1; // First digit can't be '0' for (int i = 2; i = 1 && single_digit = 10 && double_digit

[@tamils12345]

@@jst8922 thanks man.

[@imdarkseid2343]

​@@tamils12345 Bro neenga final year ah bro

[@tamils12345]

@@imdarkseid2343 no. Working

[@GmHighlight12]

What if String length only 2 this code will failed to execute

[@SevDeuceOff]

I tested with string length as 2. It works. Can you share specific examples that failed for you ?

[@GmHighlight12]

Try to run this code on leetcode all test cases won’t pass

[@SevDeuceOff]

@@GmHighlight12 It does pass all test cases. I tore the code to determine the breakage point. Looks like you may be hinting at the test case "10". Is that the one ?

[@sriyanandakuchimanchi4042]

no it will work instead of writing dp[1] like that.,,add this check if(s.charAt(0)=='0'||s.length==0||s==null){ return 0; }