Table of Contents

Question

My thought

Nothing… The problem is pretty easy, however it troubled me for a quite long time. Just follow the instruction of the problem and simulate the whole process by coding.

Points to note

The conversion between String and int
How to handle carry
Pay attention to the additional sign
Sometimes we can use char to simplify the process

Code

import java.util.Scanner;
class test
{
    static String num1;
    static int num2,num3;
    public static void input()
    {
        Scanner input = new Scanner(System.in);
        String s = input.next();
        int len = s.length();
        for(int i=0;i<len;i++)
        {
            if(s.charAt(i)==',')
            {
                num1 = s.substring(0,i);
                num2 = s.charAt(i+1)-'0';
                num3 = s.charAt(i+3)-'0';
                break;
            }
        }
        input.close();
        // System.out.println(num1);
        // System.out.println(num2);
        // System.out.println(num3);
    }

    public static void noSolution(int decimalPoint)
    {
        int IntgerNum = num2 - num3 - 1;
        while((IntgerNum--)!=0)
        {
            System.out.print("#");
        }
        System.out.print(".");
        for(int i=0;i<num3;i++)
        {
            System.out.print("#");
        }
    }

    public static void process()
    {
        //find the decimal point
        int decimalPoint  = num1.indexOf(".");
        int decimalLength = num1.length() - decimalPoint - 1;
        int integerLength = decimalPoint;
        
        //find the impossible situation
        if(decimalLength < num3 ||integerLength + 1 + num3 > num2)
        {
            noSolution(decimalPoint);
            return;
        }
        
        String newNum = num1.substring(0,decimalPoint+num3+1);

        // System.out.println(newNum);

        //convert to integer
        String tmp="";
        int newLen = newNum.length();
        for(int i=0;i<newLen;i++)
        {
            if(newNum.charAt(i)=='.') continue;
            tmp += newNum.substring(i,i+1);
        }

        int haveASign = 0;
        if(tmp.charAt(0)=='+')
        {
            haveASign = 1;
            tmp = tmp.substring(1);
        }
        else if(tmp.charAt(0)=='-')
        {
            haveASign = -1;
            tmp = tmp.substring(1);
        }

        // System.out.print(tmp);
        int intTmp = Integer.valueOf(tmp);
        //carry
        if(newLen+1<=num1.length() && num1.charAt(newLen)>'4') intTmp++; 

        String stringTmp = Integer.toString(intTmp);

        int nowLength = stringTmp.length() + 1 + Math.abs(haveASign);

        int cntOutput = 0;
        for(int i=0;i<num2-nowLength;i++)
        {
            System.out.print("#");
            cntOutput++;
        }
        if(haveASign==-1)
        {
            System.out.print("-");
            cntOutput++;
        }
        else if(haveASign==1) 
        {
            System.out.print("+");
            cntOutput++;
        }
        //print integer
        int p=0;
        for(p=0;p<num2-1-cntOutput-num3;p++)
        {
            System.out.print(stringTmp.charAt(p));
        }
        System.out.print(".");
        for(;p<stringTmp.length();p++)
        {
            System.out.print(stringTmp.charAt(p));
        }
        
    }
    public static void main(String[] args)
    {   
        input();
        process();
    }
}

Tips

`String.split(String)`

This method can be used to split a string into parts following the instruction.

When use . or | as the symbol of split position, we need to use Escapes //.
It returns a array with the satisfied arrays