String Streak

#include <iostream>
#include <cstring>
using namespace std;
const int LGMAX = 1e5;
char s[LGMAX + 5];
int N;
long long C, p2[35];
int distToNextC[LGMAX + 5];

int Solve(char ch)
{
    distToNextC[N + 1] = 32;

    for(int i = N; i >= 1; i--)
        if(s[i] != ch) distToNextC[i] = 1 + distToNextC[i + 1];
        else distToNextC[i] = 0;

    int ret = 0, l = 1, currDif = 0;
    long long currCost = 0LL;

    for(int r = 1; r <= N; r++)
    {
        if(s[r] == ch)
        {
            currDif = 0;
            ret = max(ret, r - l + 1);
            continue;
        }

        currDif++;
        if(r - l > currDif)
        {
            currCost -= p2[currDif - 1];
            currCost += p2[currDif];
        }
        else
        {
            currCost -= p2[r - l];
            currCost += p2[r - l + 1];
        }
        while(currCost > C)
        {
            int mnDist = min(distToNextC[l], r - l + 1);
            l++;

            if(mnDist == 0)
                continue;
            if(mnDist > 30)
                continue;
            else
            {
                currCost -= p2[mnDist];
                mnDist--;
                currCost += p2[mnDist];
            }
        }
        ret = max(ret, r - l + 1);
    }
    return ret;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    p2[1] = 2;
    for(int i = 2; i <= 32; i++)
        p2[i] = 2LL * p2[i - 1];
    cin >> (s + 1);
    N = strlen(s + 1);
    cin.get();
    cin >> C;
    int sol = 1;
    for(int i = 1; i <= 32; i++)
        if(p2[i] <= C) sol = i;
    for(char ch = 'a'; ch <= 'z'; ch++)
        sol = max(sol, Solve(ch));
    cout << sol << '\n';
    return 0;
}