SW练习_P2719_DP

package com.company.luogu;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.DecimalFormat;
import java.util.StringTokenizer;
public class P2719 {
  static double[][] dp;
  public static void main(String[] args) throws Exception{
      BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st=new StringTokenizer(reader.readLine());
      int n=Integer.parseInt(st.nextToken())/2;
      dp=new double[n+1][n+1];
      for (int i = 2; i <dp.length ; i++) {
          dp[i][0]=1;
          dp[0][i]=1;
      }
      for (int i = 1; i <=n ; i++) {
          for (int j = 1; j <=n ; j++) {
              dp[i][j]=dp[i-1][j]/2+dp[i][j-1]/2;
          }
      }
      DecimalFormat df=new DecimalFormat("0.0000");
      System.out.println(df.format(dp[n][n]));
      reader.close();
  }
}