数楼梯

 1 #include<cstdio>
 2 int n,al,bl,cl;
 3 int a[3000],b[3000]={1},c[3000];
 4 int main(){
 5     scanf("%d",&n);
 6     if(n==0){printf("0\n");return 0;}
 7     for(int k=1;k<=n;k++){
 8         cl=bl;
 9         for(int i=0;i<=cl;i++){
10             c[i]+=a[i]+b[i];
11             if(c[i]>9){
12                 c[i+1]+=1;
13                 c[i]%=10;
14                 if(i==cl) cl++;
15             }
16         }
17         al=bl;
18         for(int i=0;i<=al;i++) a[i]=b[i];
19         bl=cl;
20         for(int i=0;i<=bl;i++) b[i]=c[i],c[i]=0;
21     }
22     for(int i=bl;i>=0;i--)
23     printf("%d",b[i]);
24     printf("\n");
25     return 0;
26 }