一、不带数组解法 #include <iostream> using namespace std; int main() { int a; cin >> a; int b = 1 , c = 1 , d = 0 , e; if(a == 1) cout << d << endl; if(a == 2 || a == 3) cout << b << endl; if(a >= 4) { for(int i = 4;i <= a;i++) { e = b; b = b + 2 * c + d; d = c; c =...