N阶楼梯上楼问题一次可以走两阶或一阶问有多少种上楼方式非递归

include<stdio.h>
double C(int x,double s){int y;
ys-x;s1;
for(int i1;i<y;i++) s*(double)(x+i)/i;
return s;
}
int main(){
int n,x,y;double s0;
scanf("%d",&n);
for(x0;x<n/2;x++) yn-2*x,s+C(x,x+y);
printf("%.0lf",s);
}这样

很明显，有N种方法啊~~