Gas Pipeline

#include <bits/stdc++.h>
#define MAX 200005
using namespace std;

int t, n, a, b;
char c;
int thes[MAX];

int costfrom(int x, int layer) {
    if (thes[x] == 0) {
        int continuar = layer * b + a + costfrom(x+1, layer);
        int descer = layer == 2 ? costfrom(x+1, layer-1) : -1;
        int subir = layer == 1 ? cosfrom(x+1, layer+1) : -1;
        return max(max(continuar, descer), subir);
    }
}

int main() {
    cin >> t;
    for (int i = 1; i <= t; i++) {
        cin >> n >> a >> b;
        for (int j = 1; j <= n; j++) {
            cin >> c; thes[j] = c - '0';
        }
        cout << b + costfrom(0, 1) << "\n";
    }
}