uva 580 - Critical Mass(递推法！)

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

int f[31],g[31];
int n;

void pre_table()
{
    memset(f,0,sizeof(f));
    memset(g,0,sizeof(g));
    f[0]=f[1]=f[2]=0;
    g[0]=1;g[1]=2;g[2]=4;
    for(int i=3;i<=30;i++)
    {
        f[i]+=1<<(i-3);
        for(int j=2;j<=i-2;j++)
        {
            f[i]+=(g[j-2]*(1<<(i-j-2)));
        }
        g[i]=(1<<i)-f[i];
        printf("%d %d\n",i,f[i]);
    }
}

int main()
{
    pre_table();
    while(scanf("%d",&n) && n)
    {
        printf("%d\n",f
);
    }
    return 0;
}

#include<stdio.h>
int f[31]= {0,0,0,
            1,
            3,
            8,
            20,
            47,
            107,
            238,
            520,
            1121,
            2391,
            5056,
            10616,
            22159,
            46023,
            95182,
            196132,
            402873,
            825259,
            1686408,
            3438828,
            6999071,
            14221459,
            28853662,
            58462800,
            118315137,
            239186031,
            483072832,
            974791728
           };
int main()
{
    int n;
    while(scanf("%d",&n)&&n)
    {
        printf("%d\n",f
);
    }
    return 0;
}