递推 hdu 1330

http://www.cnblogs.com/rainydays/archive/2013/01/16/2862235.html

看样例的答案

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>

using namespace std;
typedef long long ll;
#define MAXN 100010
double z[MAXN];

int main()
{
    z[1]=0.5;
    for(int i=2;i<MAXN;i++)
        z[i]=z[i-1]+1.0/(i*2);
    int n;
    printf("# Cards  Overhang
");
    while(scanf("%d",&n)!=EOF)
    {
        printf("%5d%10.3lf
",n,z[n]);
    }
    return  0;
}