华为2014第三题

import java.math.BigDecimal;

import java.math.RoundingMode;

import java.util.*;



import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

import javax.security.auth.kerberos.KerberosKey;

public class Main{

    int N=8;

    int [] step=new int[N];

    String ope[]={"+","-",""};

    ScriptEngineManager manager=new ScriptEngineManager();

    ScriptEngine engine=manager.getEngineByName("js");

    private void step()

    {

        step[N-1]++;

        for(int i=N-1;i>=0;i--)

        {

            if(step[i]>2)

            {

                step[i]=step[i]%3;

                if(i!=0)

                    step[i-1]++;

            }

            else {

                break;

            }

        }

    }

    public int search() throws ScriptException

    {

          int K=(int)Math.pow(3, N);

        int count=0;

          for(int i=0;i<K;i++)

          {

              String operation="1"+ope[step[0]]+"2"+ope[step[1]]+"3"+ope[step[2]]+

                      "4"+ope[step[3]]+"5"+ope[step[4]]+"6"+ope[step[5]]+

                      "7"+ope[step[6]]+"8"+ope[step[7]]+"9";

                //Object result=engine.eval(operation);

              //double d=((Double)result).doubleValue();

                String result=sizeyunsuan(operation);

                double d=Double.parseDouble(result);

                if((int)d==5)

                {

                    count++;

                }

                step();

          }

          return count;

    }

    private static String addBigDecimal(String a,String b)

    {

        double a1=Double.parseDouble(a);

        double b1=Double.parseDouble(b);

        BigDecimal a2=BigDecimal.valueOf(a1);

        BigDecimal b2=BigDecimal.valueOf(b1);

        BigDecimal s=a2.add(b2);

        return s.toString();

    }

    private static String substractBigDecimal(String a,String b)

    {

        double a1=Double.parseDouble(a);

        double b1=Double.parseDouble(b);

        BigDecimal a2=BigDecimal.valueOf(a1);

        BigDecimal b2=BigDecimal.valueOf(b1);

        BigDecimal s=a2.subtract(b2);

        return s.toString();

    }

    private static String sizeyunsuan(String s)

    {

        //1、先将  +-*/找出来

        int p=0;//the count of (+-*/)

        for(int i=0;i<s.length();i++)

        {

            if(s.charAt(i)=='+' || s.charAt(i)=='-')

                p++;

        }

        //将字符串按照运算符进行切割总共有  2*p+1个段   example:p=5

        String[] piece=new String[2*p+1];// save pieces divided by operator   11 pieces

        int start=0,index=0;//

        for(int i=0;i<s.length();i++)

        {

            if(s.charAt(i)=='+' || s.charAt(i)=='-')

            {

                piece[index]=s.substring(start,i);//index=0  i=1  p[0]="9"

                index++;

                piece[index]=""+s.charAt(i);    //index=1  i=1  p[1]="+"

                index++;

                start=i+1;   //start=2

            }

        }

        // last piece;

        piece[index]=s.substring(start,s.length());

        ///

        int count=p;

        while(count>0)

        {

            //then calculate +-

            for(int i=0;i<piece.length;i++)

            {

                if(piece[i].equals("+") || piece[i].equals("-"))

                {

                    //find strs in piece has not calculated

                    //find strs left not equals "p"

                    int l=0;

                    for(l=i-1;l>-1;l--)

                    {

                        if(!piece[l].equals("p"))

                            break;

                    }

                    //find strs right not equals "p"

                    int r=0;

                    for(r=i+1;r<piece.length;r++)

                    {

                        if(!piece[r].equals("p"))

                            break;

                    }

                    if(piece[i].equals("+"))

                    {

                        piece[i]=addBigDecimal(piece[l], piece[r]);

                        piece[l]="p";

                        piece[r]="p";

                        count--;

                    }

                    else

                    {

                        piece[i]=substractBigDecimal(piece[l], piece[r]);

                        piece[l]="p";

                        piece[r]="p";

                        count--;

                    }

                    //break;

                }

            }

        }

        String r="";

        //find the string not equals "p"

        for(int i=0;i<piece.length;i++)

        {

            if(!piece[i].equals("p"))

            {

                r=piece[i];

                break;

            }

        }

        return r;

    }

      public static void main(String[] args) throws ScriptException{

          Main main=new Main();

          long begin=System.currentTimeMillis();

          int c=main.search();

          long end=System.currentTimeMillis();

          System.out.println(c);

          System.out.println("共花费"+(end-begin)+"ms");

      }

      

}

使用ScriptEngineManager

21

共花费637ms

使用自定义算法

21

共花费80ms