@darshancool25 Please help me out
If you have watched the official video editorial, making changes in your code shouldnt be tough !! To answer your second question, just keep practicing variety of problems. Most of the problems are new to everyone, but the one having more practice can link it with a standard problem or past problem / idea.
1 Like
what’s wrong with my code pls… help-
#include <bits/stdc++.h>
using namespace std;
int main() {
int t;
cin>>t;
while(t–)
{
int n,k;
cin>>n>>k;
string s;
cin>>s;
int q[k];
for(int i=0;i<k;i++)
{
cin>>q[i];
}
long long int count=0;
if(n==1)
{
cout<<“0”<<"\n";
}
else{
for(int i=0;i<n-1;i++)
{
if(s[i]==s[i+1])
{
count+=2;
}
else
{
count++;
}
}
for(int i=0;i<k;i++)
{
s[q[i]-1]=s[q[i]-1]^1;
if((q[i]-1)<k-1 && (q[i]-1)>0)
{
if(s[q[i]-1]!=s[q[i]-2] && s[q[i]-1]!=s[q[i]])
{
count-=2;
}
if(s[q[i]-1]==s[q[i]-2] && s[q[i]-1]==s[q[i]])
{
count+=2;
}
}
else
{
if((q[i]-1)==0)
{
if(s[q[i]-1]==s[q[i]])
{
count++;
}
if(s[q[i]-1]!=s[q[i]])
{
count--;
}
}
if((q[i]-1)==k-1)
{
if(s[q[i]-1]==s[q[i]-2])
{
count++;
}
if(s[q[i]-1]!=s[q[i]-2])
{
count--;
}
}
}
cout<<count<<"\n";
}
}}
return 0;
}
thnx for trying and helping…!
Please either format your code or (better!) link to your submission - the forum software has mangled it and it won’t compile! 
#include <bits/stdc++.h>
using namespace std;
define ll long long
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll int t;
cin>>t;
for(ll int i=0;i<t;i++)
{
ll int n,k;
cin>>n>>k;
string s;
cin>>s;
ll int a[k+1]={};
for(ll int x=1;x<=k;x++)
{
cin>>a[x];
}
ll int len=0;
for(ll int r=0;r<s.size()-1;r++)
{
// cout<<s[r]<<s[r+1]<<endl;
if(s[r]==s[r+1])
len+=2;
else
len+=1;
}
if(n==1)
{
cout<<“0”<<endl;
continue;
}
//cout<<len<<endl;
for(ll int j=1;j<=k;j++)
{
if(s[a[j]-1]==‘0’)
{
s[a[j]-1]=‘1’;
//cout<<“z”<<endl;
}
else
{
s[a[j]-1]=‘0’;
}
if(s[a[j]-1]==s[a[j]] && a[j]>1 && a[j]<k)
{
len++;
}
if(s[a[j]-1]!=s[a[j]] && a[j]>1 && a[j]<k)
{
len–;
}
if(s[a[j]-1]==s[a[j]-2] && a[j]>1 && a[j]<k)
{
len++;
}
if(s[a[j]-1]!=s[a[j]-2] && a[j]>1 && a[j]<k)
{
len–;
}
if(a[j]==1)
{
if(s[a[j]-1]==s[a[j]])
{
len++;
}
else
{
len–;
}
}
if(a[j]==k)
{
if(s[a[j]-2]==s[a[j]-1])
len++;
else
len–;
}
cout<<len<<endl;
}
}
return 0;
}
can someone tell me why my code is showing wrong answer @darshancool25
Please either format your code or (better!) link to your submission - the forum software has mangled it and it won’t compile!
1
6 4
111010
4 5 6 3
thnku vry much …!
I was doing such a silly mistake…!
1 Like
By sample test case do you mean
1
3 3
010
2 1 3`
cause it is giving right output for me in Sublime textThere’s Undefined Behaviour for you 
Can you please tell me why? I really don’t know. I only use CC IDE or Sublime Text and it’s giving correct output for both for sample test case
Out-of-Bounds accesses are Undefined Behaviour, meaning anything can happen - you might get the right answer; you might get the wrong answer; it might crash. It’s almost impossible to predict what will happen.
This is giving an output of
9
9
8
6
for meI’m so sorry! It gave AC when I did
if (s[1] != s[0] && n > 1)
I wouldn’t have gone down by a division if I corrected this.
It was failing for the simplest TC,
1
1 1
1
1
1 Like
Thank you I’ll look into it 
1 Like
Yeah it worked using pass by reference. Thank you!
1 Like
Please either format your code or (better!) link to your submission - the forum software has mangled it and it won’t compile!
Consider the test input:
1
4 8
0110
1 4 2 1 3 2 1 2