This is a video editorial on the hardest problem on codeforces round 560. The problem deals with finding number of paths in a matrix using dynamic programming, combinatorial math and inclusion-exclusion.

Feel free to post your comments below. Cheers!

Problem Statement:

Solution Code:

Inverse Modulo:

Combinatorics:

Dynamic Programming:

Nguồn: https://dothihoa.com

Xem thêm bài viết khác: https://dothihoa.com/cong-nghe

Thanks for this, wonderful explanation. I submitted the code with this approach but still, I get Time Limit Exceed on test case 7. Any lead on how to resolve it will be helpful. I do regular programming on CodeChef but I am pretty new to Codeforces.

How, total no. of paths from (0,0) to (i,j) is i+j C i, considering no black cell encounter?

I dont know that language. What is name of that language?

I almost exploxed, but i get it

May be its similar to rate in a maze problem.

Exactly rat in a maze problem

Hey. Please make a video on Suffix Tree automation…

I did it w/o using combinations , what I did was

iterate through each element in the 2D integer array(which can be done while filling true or false in a boolean array ..black for false and white for true).. so I will be having 2 different arrays one boolean and other integer , now if ( boolean_array[i][j]==false)

which means it is a black cellthen integer_array[i][j]=trueelse do the following

if i==0 and j==0

then integer_array[i][j]=0

integer_array[i][j]=integer_array[i-1][j]+integer_array[i][j-1] also check for 0th row or 0th column index respectively …at last the last element of the 2-D array will have the answer .. basically I have used a DP approach … Is it correct ?

Really enjoy this problem 😀

but you dont do codeforces solutions anymore?

thanks for sharing this problem 🙂

Hey Gaurav ! I really need your help!

I started practicing on codechef and everytime I submit a problem ,I get a time-exceeded error.The output is correct but this error just doesn't seem to go whichever method I use(recursion ,DP,etc).I read online and used scanf,printf instead of cin,cout ,but I still am getting a Time limit error.I am wasting hours on a simple problem because of this.

please go through my code:

Question: https://www.codechef.com/problems/PALIN

#include <iostream>

#include <algorithm>

#include<vector>

#include <string>

using namespace std;

bool is_palin(long long int num);

long long int next_palin(long long int n);

int main()

{

int t;

cin>>t;

vector<long long int> a;

long long int n;

for(int i=0;i<t;i++)

{

cin>>n;

a.push_back(next_palin(n));

}

for(int i=0;i<a.size();i++)

{

cout<<a[i]<<endl;

}

}

bool is_palin(long long int n)

{

string s = to_string(n);

int len=s.length();

for(int i=0;i<len/2;i++)

{

if(s[i]!=s[len-i-1])

return false;

}

return true;

}

long long int next_palin(long long int n)

{

while(1)

{

bool var=is_palin(n);

if(var==true)

break;

else n++;

}

return n;

}

There is more more problem which I solved using both DP and recursion but getting the same error.

Great video.

Great channel.

Keep em coming.

Thanks

Hello sir,

I want a suggestion. Actually, I am practicing beginner level questions on codeshef. I am in Btech 3rd sem, and still I am struggling with beginner level questions. Please suggest me or help to do it in a better way because it is sometimes frustrating when I am not able to solve those problems.

Hey Gaurav, what was your interview process with Directi like? Directi in my college only offers upto application engineer profile, how did you get a call for platform engineer? Frcrce rocks(except the rules)

Greetings Sir,

I am confused as to which language I should choose for competitive coding

(1)Python

Or (2)C++

Please give your valuable comments and suggest best language for competitive coding purpose

Thanks in advance 😊😊

Hey Gaurav, I stumbled upon your channel while searching for CP. I'm in class 11 with Java, how do you suggest I get started with CP? I love simple programming, but a senior suggested that I try CP. We have just started 2D Array in school. Thanks.

nice one👍

Hey man, Can you explain why some problems say to do ANS%10^9+7 something like that?

Thank You bhaiya…your videos help me alot….Can u make series or episodes On how to solve graph/trees problem in JAVA with code

hey man uh r just awsm….