[BOJ] 15988 : 1, 2, 3 더하기 3

#include <cstdio>
int n, t, d[1000001]={0,1,2,4};
int main() {
    for (int i = 4; i <= 1e6; i++) {
        d[i] = ((long long)d[i-1]+d[i-2]+d[i-3]) % (int)(1e9+9);
    }
    for (scanf("%d", &t); t--;) {
        scanf("%d", &n);
        printf("%d\n", d[n]);
    }
    return 0;
}