景驰第二题求助。。。 int main() { int n; cin >> n; int re; if (n <= 1) re = 0; else if (n == 2) re = 3; else { re = 0; vector<int> dp(n + 1, 0); for (int i = 2;i <= n;i++) { dp[i] = i + 1; for (int j =...