Codeforces Round #797 (Div. 3) 1690D - Black and White Stripe Solution

 

Problem Link:  https://codeforces.com/contest/1690/problem/D

Solution in C++:

///La ilaha illellahu muhammadur rasulullah

///******Bismillahir-Rahmanir-Rahim******///

///Abul Hasnat  Tonmoy

///Department of CSE,23rd batch

///Islamic University,Bangladesh

///**********ALLAH IS ALMIGHTY************///

#include <bits/stdc++.h>

using namespace std;

int main()

{

    int  n,x,t,r,k,i,mn;

    cin>>t;

    while(t--)

    {

        cin>>n>>k;

        x=0;

        string s;

        cin>>s;

        for(i=0; i<k; i++)

        {

            if(s[i]=='W')

                x++;

        }

        mn=x;

        for(i=k;i<n; i++)

        {

            if(s[i-k]=='W')

                x--;

            if(s[i]=='W')

                x++;

            mn=min(x,mn);

        }

        cout<<mn<<endl;

    }

    return 0;

}