[hdu2156]分数矩阵

#include <stdio.h>
double dp[50001];
int main(){
    int n;
      dp[1]=1;
      dp[2]=3;
      
      for(int i=3;i<=50000;i++){
          dp[ i ] = 2 * dp[ i - 1 ] - dp[ i - 2 ] + ( 2.0 / i );
    }
    while(scanf("%d",&n)==1 && n){
        printf("%.2lf\n",dp[n]);
    }
}

import java.util.Scanner;

public class Main {

    public static double[] dp = new double[ 50001 ];

    public static void dp() {
        dp[ 1 ] = 1;
        dp[ 2 ] = 3;
        for( int i = 3; i <= 50000; i++ ) {
            dp[ i ] = 2 * dp[ i - 1 ] - dp[ i - 2 ] + ( 2.0 / i );
        }
    }

    public static void main( String[] args ) {
        Scanner sc = new Scanner( System.in );
        dp();
        while( sc.hasNext() ) {
            int n = sc.nextInt();
            if( n == 0 )
                return;
            else {
                System.out.printf( "%.2f\n", dp[ n ] );
            }
        }
    }
}