题解

#include <iostream>
using namespace std;

int main() {
    int N, M;
    cin >> N >> M;
    long long dp[20][20];
    for (int i = 0; i < N; i++) {
        dp[i][0] = 1;
    }
    for (int j = 0; j < M; j++) {
        dp[0][j] = 1;
    }
    for (int i = 1; i < N; i++) {
        for (int j = 1; j < M; j++) {
            dp[i][j] = dp[i-1][j] + dp[i][j-1];
        }
    }
    cout << dp[N-1][M-1] << endl;
	return 0;
}

万恶的DP