UVALive 6661 解题心得

#include<iostream>
#include<cstdio>
using namespace std;

int n, k, sum;
int cnt = 0;
int depth=0;

void dfs(int dep, int cur_num, int cur_sum)
{
    //depth++;
     if (cur_sum == sum)        return;
    for (int i = cur_num; i <= n; i++)
    {
        if (cur_sum+i>sum)            return;
        if (cur_sum+i == sum&&dep==k)
        {
            cnt++;    return;
        }
        dfs(dep + 1, i + 1, cur_sum + i);
    }
}

int main()
{
    while (cin >> n >> k >> sum&&n != 0)
    {
        depth = 0;
        cnt = 0;
        dfs(1, 1, 0);
        cout << cnt << endl;
    }
    

    return 0;
}