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Codeforces Round #112 (Div. 2)(C. Another Problem on Strings)


 Bismillahir Rahmanir Rahim

///Author: Tanvir Ahmmad
///CSE,Islamic University,Bangladesh

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<string>
#include<cstring>
#include<sstream>
#include<cmath>
#include<cstring>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<vector>
#include<iterator>
#include <functional> ///sort(arr,arr+n,greater<int>()) for decrement of array
/*every external angle sum=360 degree
  angle find using polygon hand(n) ((n-2)*180)/n*/
///Floor[Log(b)  N] + 1 = the number of digits when any number is represented in base b
using namespace std;
typedef long long ll;

int main()
{
    ll n,cnt=0,bro=0;
    map<ll,ll>mp;
    map<ll,ll>::iterator it;
    string str;
    cin>>n>>str;
    if(n)
    {
        ll sz=str.size(),arr[sz+3],k=0;
        for(ll i=0; i<sz; i++)
        {
            if(str[i]=='1')
                arr[k++]=i,mp[i]=bro,bro=0;
            else
                bro++;
        }
        arr[k++]=sz,mp[sz]=bro;
        for(ll i=0; i<k-n; i++)
        {
            ll pre=arr[i],post=arr[i+n];
            it=mp.find(pre);
            ll cnt_pre=it->second;
            it=mp.find(post);
            ll cnt_post=it->second;
            if(max(cnt_post,cnt_pre)==0)
                cnt++;
            else if(min(cnt_post,cnt_pre)==0 && max(cnt_post,cnt_pre)!=0)
                cnt+=(max(cnt_post,cnt_pre)+1);
            else
                cnt+=(1+cnt_pre+cnt_post+(cnt_pre*cnt_post));
        }
        cout<<cnt<<endl;
    }
    else
    {
        for(ll i=0;i<str.size();i++) 
        {
            if(str[i]=='0') bro++;
            else cnt+=(bro*(bro+1)/2),bro=0;
        }
        if(bro) cnt+=(bro*(bro+1)/2),bro=0;
        cout<<cnt<<endl;
    }
    return 0;
}
///Alhamdulillah

Problem Link:https://codeforces.com/problemset/problem/165/C

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