逆向思维 从下面向上递推

参考代码

const int N = 100009;
int n, s[N];
void solve()
{
    cin >> n;
    for (int i = 2; i < (1 << (n + 1)); i++)
        cin >> s[i];
    int ans = 0;
    for (int i = 1 << (n + 1) - 1; i >= 1; i--)
    {
        int l = i * 2, r = i * 2 + 1;
        ans += max(s[l], s[r]) * 2 - s[l] - s[r];
        s[i] += max(s[l], s[r]);
    }

    cout << ans << '\n';
}