uva 580 Critical Mass(递推)

#include<stdio.h>#include<algorithm>#include<string.h>#include<iostream>using namespace std;typedef unsigned long long ull;int main(){    int i,j,n;    ull f[35],a[35],g[35];    a[0]=1;    for(i=1;i<=30;i++)    {        a[i]=a[i-1]*2;    }    f[0]=f[1]=f[2]=0;    g[0]=1;g[1]=2;g[2]=4;    for(i=3;i<=30;i++)    {        f[i]=a[i-3];        for(j=2;j<=i-2;j++)        {            f[i]+=g[j-2]*a[i-j-2];        }        g[i]=a[i]-f[i];    }    while(~scanf("%d",&n)&&n)    {        cout<<f[n]<<endl;    }    return 0;}