【正经题解-男生女生排排队】

很水

#include <bits/stdc++.h>
using namespace std;
long long dp[85][3];
int main()
{
    int n;
    cin >> n;
    dp[1][0] = 1;
    dp[1][1] = 1;
    dp[1][2] = 0;
    for (int i = 2; i <= n; i++)
    {
        dp[i][0] = dp[i - 1][0] + dp[i - 1][2];
        dp[i][1] = dp[i - 1][0];
        dp[i][2] = dp[i - 1][1] + dp[i - 1][2];
    }
    cout << dp[n][0] + dp[n][2];
    return 0;
}

能AC