题解 | 小红走矩阵

#include <iostream>
#include <vector>
using namespace std;
#define ll long long

int main() {
    int n, m;
    cin >> n >> m;
    vector<vector<ll>> dp(n, vector<ll>(m));
    
    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]) % 998244353; 
        }
    }
    cout << dp[n - 1][m - 1] << endl;

    return 0;
}