DFS

#include<iostream>
using namespace std;

const int N = 15;

int t, m, n, ans;
int st[N];

void dfs(int u, int k)
{
    if (u > n+1 || k > m) return;
    if (u == n+1 && k == m)
    {
        ans++;
        return;
    }
    for (int i = st[u-1]; i <= m; i++)
    {
        st[u] = i;
        dfs(u+1, k+i);
        st[u] = 0;
    }
}

int main()
{
    cin >> t;
    while (t--)
    {
        cin >> m >> n;
        ans = 0;
        dfs(1, 0);
        cout << ans << endl;
    }

    return 0;
}