hdu4933 Miaomiao's Function

水水的计数题，关键在细节。

import java.math.BigInteger;
import java.util.Scanner;
import java.io.*;

public class Main {
    BigInteger n0 = BigInteger.valueOf(0);
    BigInteger n1 = BigInteger.valueOf(1);
    BigInteger n2 = BigInteger.valueOf(2);
    BigInteger n10 = BigInteger.valueOf(10);
    BigInteger n9 = BigInteger.valueOf(9);
    BigInteger rev = BigInteger.valueOf(-1);
    BigInteger n45 = new BigInteger("45");
    BigInteger p[] = new BigInteger [110];
    BigInteger P[] = new BigInteger [110];
    BigInteger dP[] = new BigInteger [110];
    BigInteger M[] = new BigInteger [110];
    void init(){
        dP[0] = P[0] = p[0] = n0;
        M[0] = n1;
        for(int i = 1; i < 102; i++){
            //System.out.println(i);
            p[i] = M[i - 1].multiply(n45);
            p[i] = p[i].subtract(n9.multiply(P[i - 1]));
            //System.out.println(p[i]);
            //System.out.println("ok");
            P[i] = p[i].subtract(P[i - 1]);
            dP[i] = dP[i - 1].add(p[i]);
            M[i] = M[i - 1].multiply(n10);
            //System.out.println("M" + i + "  " + M[i]);
        }
    }
    
    BigInteger getAns(BigInteger num){
        if(num.equals(n0)) return n0;
        if(num.compareTo(n0) > 0 && num.compareTo(n9) <= 0) return num.add(n1).multiply(num).divide(n2);
        String str = num.toString();
        int len = str.length();
        BigInteger first = num.divide(M[len - 1]);
        BigInteger new_num = num.mod(M[len - 1]);
        BigInteger tem = dP[len - 1];
        //System.out.println("tem" + tem);
        tem = tem.add(M[len - 1].multiply(first.multiply(first.subtract(n1)).divide(n2)));
        tem = tem.subtract((first.subtract(n1)).multiply(P[len - 1]));
        tem = tem.add(new_num.add(n1).multiply(first));
        if(new_num.equals(n0)) return tem;
        BigInteger sign = n1;
        int tmp = len - 1;
        while(new_num.divide(M[tmp]).equals(n0)){
             tmp--;
             sign = sign.multiply(rev);
        }
        while(new_num.compareTo(n0) > 0){
            //System.out.println("tem " + tem);
            //System.out.println("new_num" + new_num);
            String new_str = new_num.toString();
            int new_len = new_str.length();
            BigInteger new_sign = (len - 1) % 2 == 0 ? n1 : rev;
            int i = 1;
            //System.out.println("new_len" + new_len);
            while(i < new_len){
                tem = tem.add(new_sign.multiply(p[i]));
                //System.out.println("i" + i + "p[i]" + p[i] + "tem" + tem);
                new_sign = new_sign.multiply(rev);
                i++;
            }
            //System.out.println("ok");
            //System.out.println("new_sign" + new_sign);
            BigInteger new_first = new_num.divide(M[new_len - 1]);
            tem = tem.add(new_first.subtract(n1).multiply(new_first).divide(n2).multiply(M[new_len - 1]).multiply(new_sign));
            //System.out.println("tem" + tem);
            tem = tem.add(new_sign.multiply(rev).multiply(new_first.subtract(n1)).multiply(P[new_len - 1]));
            //System.out.println("tem" + tem);
            new_num = new_num.mod(M[new_len - 1]);
            tem = tem.add(new_first.multiply(n1.add(new_num)).multiply(new_sign));
        }
        return tem;
    }
    
    BigInteger f(BigInteger num){
        if(num.compareTo(n0) < 0){
            BigInteger tem = num.divide(n9);
            num = num.add(tem.multiply(n9).multiply(rev));
            while(num.compareTo(n0) > 0) num = num.subtract(n9);
            while(num.compareTo(n0) <= 0) num = num.add(n9);
        }
        if(num.compareTo(n0) >= 0 && num.compareTo(n9) <= 0) return num;
        BigInteger tem = n0;
        while(num.compareTo(n0) > 0){
            tem = tem.add(num.mod(n10));
            num = num.divide(n10);
        }
        return f(tem);
    }
    
    void solve(){
        Scanner cin = new Scanner(System.in);
        int T = cin.nextInt();
        while(T-- != 0){
            String stra = cin.next();
            String strb = cin.next();
            BigInteger a = new BigInteger(stra);
            BigInteger b = new BigInteger(strb);
            BigInteger front = a.equals(n0) ? n0 : getAns(a.subtract(n1));
            BigInteger rear = getAns(b);
            //System.out.println("rear" + rear);
            BigInteger ans = rear.subtract(front);
            BigInteger fAns = f(ans);
            if(fAns.equals(n0)) System.out.println("Error!");
            else{
                // System.out.println("ans" + ans);
                //System.out.println("fAns" + fAns);
                ans = ans.mod(fAns).add(fAns).mod(fAns);
                System.out.println(ans);
            }
        }
        cin.close();
    }
    public static void main(String[] args) throws IOException{
        Main e = new Main();
        e.init();
        e.solve();
    }
}