DouKaku?

using System;
using System.Collections.Generic;
static class Program {
    static void Main(String[] args) {
        int n = int.Parse(args[0]), m = int.Parse(args[1]);
        List<int[]> result = new List<int[]>();
        Append(result, n, m, 0, new int[0]);
        result.Sort(delegate(int[] x, int[] y) {
            for(int i = 0; i < x.Length; i++) {
                if (x[i] != y[i]) {
                    return x[i].CompareTo(y[i]) * -1;
                }
            }
            return 0;
        });
        foreach(int[] res in result) {
            Console.WriteLine(string.Join(", ", Array.ConvertAll<int, string>(res,
                delegate(int x) { return x.ToString(); })));
        }
    }
    static void Append(List<int[]> result, int n, int m, int sum, int[] items) {
        if (m <= items.Length) {
            if (n == sum) {
                result.Add(items);
            }
        }
        else {
            List<int> temp = new List<int>(items);
            temp.Add(0);
            for(int i = 0; i + sum <= n; i++) {
                temp[temp.Count - 1] = i;
                Append(result, n, m, sum + i, temp.ToArray());
            }
        }
    }
}