CHARGES - Editorial

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

whatā€™s wrong with my code plsā€¦ help-
#include <bits/stdc++.h>
using namespace std;

int main() {
int t;
cin>>t;
while(tā€“)
{
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<<ā€œ0ā€<<"\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 helpingā€¦!

Please either format your code or (better!) link to your submission - the forum software has mangled it and it wonā€™t compile! :slight_smile:

#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<<ā€œ0ā€<<endl;
continue;
}
//cout<<len<<endl;
for(ll int j=1;j<=k;j++)
{
if(s[a[j]-1]==ā€˜0ā€™)
{
s[a[j]-1]=ā€˜1ā€™;
//cout<<ā€œzā€<<endl;
}
else
{
s[a[j]-1]=ā€˜0ā€™;
}
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)
{
lenā€“;
}
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)
{
lenā€“;
}
if(a[j]==1)
{
if(s[a[j]-1]==s[a[j]])
{
len++;
}
else
{
lenā€“;
}
}
if(a[j]==k)
{
if(s[a[j]-2]==s[a[j]-1])
len++;
else
lenā€“;
}
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 wonā€™t compile! :slight_smile:

https://www.codechef.com/viewsolution/47363078
the link

1 Like
1
6 4
111010
4 5 6 3

thnku vry much ā€¦!
I was doing such a silly mistakeā€¦!

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 text

Thereā€™s Undefined Behaviour for you :man_shrugging:

Can you please tell me why? I really donā€™t know. I only use CC IDE or Sublime Text and itā€™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. Itā€™s almost impossible to predict what will happen.

This is giving an output of

9
9
8
6
for me

Iā€™m so sorry! It gave AC when I did

if (s[1] != s[0] && n > 1)

I wouldnā€™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 Iā€™ll look into it :slight_smile:

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 wonā€™t compile! :slight_smile:

Code link

Can anyone plzz tell my errorā€¦i have used the similar approachā€¦!!

Consider the test input:

1
4 8
0110
1 4 2 1 3 2 1 2

I think the case where n==1 is a pretty misleading one and should have been clearly mentioned in the question itself. My output was set to print ā€˜kā€™ times as it should be but if n==1, print should be ā€˜0ā€™ once and NOT ā€˜kā€™ times. I only understood this after watching the discussions. This was not mentioned in the video editorial even. :cry: