题解

#include<bits/stdc++.h>
using namespace std;

const int maxn = 40;
int dp[maxn][maxn];

int main() {
	
	int n, m; 
	cin >> n >> m;
	dp[0][1] = 1;
	for(int i = 1; i <= m; i++) {
		for(int j = 1; j <= n; j++) {
			int l = j - 1;
			int r = j + 1;
			if(l == 0) l = n; 
			if(r == n + 1) r = 1; 
			dp[i][j] = dp[i-1][l] + dp[i-1][r];
		}
	} 
	cout << dp[m][1];  

	return 0;
}

经典dp