D2. Sum over all Substrings (Hard Version)

原题链接

题解

code

#include<bits/stdc++.h>
#define ll long long
using namespace std;

ll dp[1000005] = {0};

void solve() {
    ll n, ans = 0;
    cin >> n;
    string s;
    cin >> s;
    s = " " + s;  // 使字符串1索引化
    for (ll i = 1; i <= n; i++) {
        if (s[i] == '1') {
            if (i > 3) {
                dp[i] = 1 + 1 + 1 + dp[i-3] + 1*(i-3);
            }
            else dp[i] = i;
        }
        else dp[i] = dp[i-1];
        ans += dp[i];
    }
    cout << ans << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    ll t = 1;
    cin >> t;
    while (t--) solve();
    return 0;
}