Bittijono

#include<bits/stdc++.h>

typedef long long ll;
using namespace std;

int n, a, b;
string s1, s2;

struct X {
    ll x;
    ll m;
    int l;
};

X d[101010];

X seuraava(const X& e, int k) {
    ll nx = e.x + k;
    return {
        nx,
        max(e.m,nx),
        e.l+1
    };
}

bool comp(const X& a, const X& b) {
    return a.x < b.x;
}

int main(){
    cin >> n >> a >> b >> s1 >> s2;

    if (s1 == s2) {
        cout << "0\n";
        return 0;
    }

    const X x1 = {1,1,1};
    const X x2 = {0,0,1};
    d[0] = {0,0,0};
    ll s = 0, u = 0;
    for (int i = 1; i <= n; i++) {
        if (s1[i-1] != s2[i-1]) {
            s++;
            d[i] = max(x1, seuraava(d[i-1],1), comp);
        }else {
            d[i] = max(x2, seuraava(d[i-1],-1), comp);
            if ((d[i].m-d[i].x)*a>b) {
                d[i] = x2;
            }
        }
    }

    /*for (int i = 1; i <= n; i++) {
        cout << d[i].x << "/" << d[i].m << "/" << d[i].l << "\n";
    }*/

    int i = n;
    while (i > 0 && d[i].l != -1) {
        if (d[i].m*a > b) {
            s -= d[i].m;
            u++;
        }
        i -= d[i].l;
    }
    /*cout << "s: " << s << "\n";
    cout << "u: " << u << "\n";*/
    cout << s*a+u*b << "\n";
}

Test 1 (public)

Group: 1, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 3

Verdict: ACCEPTED

Test 4

Group: 1, 3

Verdict: ACCEPTED

Test 5

Group: 1, 3

Verdict: ACCEPTED

Test 6

Group: 3

Verdict: ACCEPTED

Test 7

Group: 2, 3

Verdict: ACCEPTED

Test 8

Group: 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 2, 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 1, 2, 3

Verdict: ACCEPTED

Test 17

Group: 1, 3

Verdict: ACCEPTED

Test 18

Group: 1, 3

Verdict: ACCEPTED

Test 19

Group: 3

Verdict: ACCEPTED

Test 20

Group: 3

Verdict: ACCEPTED