上楼梯

#include<stdio.h>
int zha(int, int);
int zhb(int, int, int);
int main()
{
    int a, b, c,i,j=0,k,n,q[100],w[100],e[100],s=0;
    scanf("%d", &n);
    for (a = 0; a <= 6; a++)
    {
        for (b = 0; b <= 10; b++)
        {
            for (c = 0; c <= 20; c++)
            {
                if (3 * a + 2 * b + c == n)
                {
                    j++;
                    q[j] = a;
                    w[j] = b;
                    e[j] = c;
                }
            }
        }
    }
    for (i = 1; i <= j; i++)
    {
        if (q[i] == 0 && w[i] == 0 && e[i] != 0 || q[i] == 0 && w[i] != 0 && e[i] == 0 || q[i] != 0 && w[i] == 0 && e[i] == 0)
            s++;
        else if (q[i] == 0 && w[i] != 0 && e[i] != 0)
            s = s + zha(w[i], e[i]);
        else if (q[i] != 0 && w[i] != 0 && e[i] == 0)
            s = s + zha(w[i], q[i]);
        else if (q[i] != 0 && w[i] == 0 && e[i] != 0)
            s = s + zha(q[i], e[i]);
        else
            s = s + zhb(q[i], w[i], e[i]);
    }
    printf("%d", s);
}

int zha(int m, int n)
{
    int t;
    if (m < n)
    {
        t = m;
        m = n;
        n = t;
    }
    if (n == 1)
        t = m + 1;
    else if (n == 2)
        t = m + 1 + (m + 1) * m / 2;
    else if (n == 3)
        t = m + 1 + (m + 1) * m + (m + 1) * m * (m - 1) / 6;
    else if (n == 4)
        t = m + 1 + (m + 1) * m * 3 / 2 + (m + 1) * m * (m - 1) / 2 + (m + 1) * m * (m - 1) * (m - 2)/24;
    else if (n == 5)
        t = m + 1 + 2 * (m + 1) * m + (m + 1) * m * (m - 1) + (m + 1) * m * (m - 1) * (m - 2) / 6 + (m + 1) * m * (m - 1) * (m - 2) * (m - 3) / 120;
    else
        t = m + 1 + (m + 1) * m * 5 / 2 + (m + 1) * m * (m - 1) * 5 / 3 + (m + 1) * m * (m - 1) * (m - 2) * 5 / 12 + (m + 1) * m * (m - 1) * (m - 2) * (m - 3) / 24 + (m + 1) * m * (m - 1) * (m - 2) * (m - 3) * (m - 4) / 720;
    return t;
}

int zhb(int f, int g, int h)
{
    int y;
    if (f < g)
    {
        y = f;
        f = g;
        g = y;
    }
    if (g < h)
    {
        y = g;
        g = h;
        h = y;
    }
    if (f < g)
    {
        y = f;
        f = g;
        g = y;
    }
    y = zha(f, g) * zha(f + g, h);
    return y;
}