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();
     }
 }