组合问题

N个数中选M个数的组合问题

#define N 5
#define M 4
char answer[N];

void Print(char a[], int n)
{
    for (int i=0; i<n; i++)
    {
        cout << a[i] << " ";
    }
    cout << endl;
}

void Combination(char a[], int b, int n, int k)
{
    if (k == 0)
    {
        Print(answer, M);
        return;
    }
    if (k==n)
    {
        while(k>0)
            answer[--k] = a[b++];
        Print(answer,M);
        return;
    }
    answer[k-1] = a[b];
    Combination(a, b+1, n-1,k-1);
    Combination(a, b+1, n-1, k);
}
int main(int argc, char* argv[])
{
    char a[N] = {'a','b','c', 'd', 'e'};
    Combination(a, 0, N, M);
    
    return 0;
}