题解 | 牛牛学数列5

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;

    if (n == 1 || n == 2) {
        cout << 1 << endl;
        return 0;
    }

    int prev1 = 1;  // F(n-1)
    int prev2 = 1;  // F(n-2)
    int current;    // F(n)

    for (int i = 3; i <= n; ++i) {
        current = prev1 + prev2;
        prev2 = prev1;
        prev1 = current;
    }

    cout << current << endl;
    return 0;
}
// 64 位输出请用 printf("%lld")输出请用 printf("%lld")