백준 10844번 C++ 풀이

#include <iostream>
#include <algorithm>
#include <numeric>
using namespace std;

long long buffer[102][10];
int main() {

    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin >> n;
    buffer[1][0] = 0;
    for (int i = 1; i < 10; i++){
        buffer[1][i] = 1;
    }
    if (n > 1) {
        for (int i = 2; i <= n; i++) {
            for (int j = 0; j < 10; j++) {
                if (j == 0) {
                    buffer[i][0] = buffer[i - 1][1];
                } else if (j == 9) {
                    buffer[i][9] = buffer[i - 1][8];
                } else {
                    buffer[i][j] = (buffer[i - 1][j + 1] + buffer[i - 1][j - 1] )% 1000000000;
                }
            }
        }
    }
    long long sum = 0;
    for (int i = 0; i<10; i++){
        sum += buffer[n][i];
    }
    cout << sum % 1000000000;
    return 0;
}