This was my first contest and so I want to check solution of second problem.Any help?

Please wait for editorials.else u can check other’s solution.

Hey you can always check editorial here and also visit the contest page…they are available.

Welcome to Codechef Community ! After every contest Codechef releases Editorials ( explanation of the solution to problem ) and makes the submission of others users public( i.e. you can see other people’s code.)

For Editorial check this : https://discuss.codechef.com/questions/96597/abrepeat-editorial

Second problem had weird timing problem, it got AC using C string than C++ string object, with C++ string object it causes TLE.

My Solution: https://www.codechef.com/viewsolution/13381425

ANSWER=S1+S2.

S1=no. of ab pairs in string s * k

S2:

for this to calculate possible cases are all a’s will take all b’s in s and this can happen in k cases and this cases decreases to 1 eventually so basically

S2=no. of a*no. of b*(k*(k-1))/2

Plz comment if you did not understand

This problem had a nice use of concept of arithmetic progression (for those with mathematical perspectives).

I used the observations from sample cases to derive it. How did you guys approach the problem? Any other alternate, nice approach?

@vijju123 I used this approach

```
for(ll i=0;i< n;i++)
{
if(s[i]=='a')
{
ca++;
}
else if(s[i]=='b')
{
cb++;
m=m+ca;
}
}
ll ans=m*k+(ca*cb*k*(k-1))/2;
cout<< ans<< endl;
```

I don’t know whether it is nice or not but this came tp my mind

Thank you.

Thank you.

I used diff idea than your’s

Fixed the format. BTW, can you explain what you are trying to do? I am unable to understand “ll ans=m x k+(ca x cb x k x(k-1))/2;”

consider string s= abcb and k=x

so the string becomes S=s1+s2+s3+…+sx

now first i calculate ab’s in s and this repeats k times therefore count is no. of ab * k

then all “a”'s in s1 can use all the “b”'s in s2 and s3…sx

which gives a count of no. of “a”* no. of b’s * k

next all “a”'s in s2 can use all “b”'s in s3,…sx which gives a count of

no. of “a” * no. of “b” * (k-1)

continue like this …

we come to an end with formula

answer=no. of ab in s * k+ no. of “a” *no. of “b” * k *(k-1)/2.

I also used a similar approach. The concepts are same. Thanks for sharing

Sorry for my english I might have frustrated you but this is first time i am using forum so little excited

https://www.codechef.com/viewsolution/13381425 I used this, little different idea than in editorial, I updated the link,

Thanks for the link. I think saisurya also did something similar. What was your thinking? Meaning, what trick you found in the question which made you take that approach?

For me it was presence of an AP with d=Number of 'b’s in the string.