C. Пара последовательностей с одинаковой суммой

#include <iostream>
#include <vector>
#include <map>
using namespace std;


int main() {
    int n; cin >> n;
    vector <int> a(n), b(n), pfa(n), pfb(n);
    for (int &el: a) cin >> el;
    pfa[0] = a[0];
    for (int i = 1; i < n; ++i) {
        pfa[i] = pfa[i - 1] + a[i];
    }
    for (int &el: b) cin >> el;
    pfb[0] = b[0];
    for (int i = 1; i < n; ++i) {
        pfb[i] = pfb[i - 1] + b[i];
    }
    if (pfa[n - 1] == pfb[n - 1]) {
        cout << n << "\n";
        exit(0);
    }
    vector <int> dif(n);
    for (int i = 0; i < n; ++i) {
        dif[i] = pfa[i] - pfb[i];
    }
    map <int, int> met;
    met[0] = -1;
    int ans = 0;
    for (int i = 0; i < n; ++i) {
        if (met.find(dif[i]) != met.end()) {
            ans = max(ans, i - met[i] + 1);
        } else {
            met[dif[i]] = i;
        }
    }
    cout << ans << "\n";
}