HDU 4933 Miaomiao's Function(数位DP + 高精度)

题目连接 ： http://acm.hdu.edu.cn/showproblem.php?pid=4933

题意 ： 自己看吧，还是很容易理解的，就一个公式而已。

方法 ： 比赛的时候想到两次数位DP：先对所有的数进行一次mod9 的数位DP,再得出的答案x为新的mod，再进行一次mod，后来写着写着发现似乎有点问题，对于answer = 0要特判，然后没想到好的方法，比赛就结束了。

赛后用java写了一发大数过的，对于题解中用多个大质数去判这种神奇的作法只能意会下了 ， 貌似rand() 也行？

  1 import java.io.*;
  2 import java.util.*;
  3 import java.math.*;
  4
  5 public class Main {
  6
  7     /**
  8      * @param args
  9      */
 10     public static class Pair {
 11         BigInteger cnt, sum;
 12     }
 13
 14     public static BigInteger sum[][] = new BigInteger[105][3];
 15     public static BigInteger cnt[][] = new BigInteger[105][3];
 16     public static int bit[] = new int[105];
 17     public static boolean vis[][] = new boolean[105][3];
 18
 19     public static Pair dfs(int len, int dis, boolean fp) {
 20         //System.out.println(len + " " + s + " " + dis + " " + fp);
 21         Pair ret = new Pair();
 22         if (len == 0) {
 23             ret.cnt = BigInteger.ONE; ret.sum = BigInteger.ZERO;
 24             return ret;
 25         }
 26         if (fp == false && vis[len][dis] == true) {
 27             ret.cnt = cnt[len][dis];
 28             ret.sum = sum[len][dis];
 29             return ret;
 30         }
 31         int Max;
 32         BigInteger Sum = BigInteger.ZERO;
 33         BigInteger Cnt = BigInteger.ZERO;
 34         if (fp == true) Max = bit[len];
 35         else Max = 9;
 36         //System.out.println("Max = " + Max);
 37         for (int i = 0; i <= Max; i++) {
 38             if (i > 0) {
 39                 if (dis == 0 || dis == 1) {
 40                     ret = dfs(len-1, 2, fp==true&&i==Max);
 41                     Cnt = Cnt.add(ret.cnt); Sum = Sum.add(ret.sum);
 42                     Sum = Sum.add(ret.cnt.multiply(BigInteger.valueOf(i)));
 43                 }else {
 44                     ret = dfs(len-1, 3-dis, fp==true&&i==Max);
 45                     Cnt = Cnt.add(ret.cnt); Sum = Sum.add(ret.sum);
 46                     Sum = Sum.subtract(ret.cnt.multiply(BigInteger.valueOf(i)));
 47                 }
 48             }else {
 49                 if (dis == 0) {
 50                     ret = dfs(len-1, dis, fp==true&&i==Max);
 51                     Cnt = Cnt.add(ret.cnt); Sum = Sum.add(ret.sum);
 52                 }else {
 53                     ret = dfs(len-1, 3-dis, fp==true&&i==Max);
 54                     Cnt = Cnt.add(ret.cnt); Sum = Sum.add(ret.sum);
 55                 }
 56             }
 57         }
 58         if (fp == false) {
 59             vis[len][dis] = true;
 60             sum[len][dis] = Sum;
 61             cnt[len][dis] = Cnt;
 62         }
 63         ret.cnt = Cnt; ret.sum = Sum;
 64         return ret;
 65     }
 66     public static BigInteger solve(BigInteger x) {
 67         if (x.equals(BigInteger.valueOf(-1))) return BigInteger.ZERO;
 68         String tmp = String.valueOf(x);
 69         for (int i = 0; i < tmp.length(); i++) {
 70             bit[i+1] = tmp.charAt(tmp.length() - i - 1) - ‘0‘;
 71         }
 72         return dfs(tmp.length(), 0, true).sum;
 73     }
 74     public static void main(String[] args) {
 75         // TODO Auto-generated method stub
 76         Scanner cin = new Scanner(System.in);
 77         int T = cin.nextInt();
 78         for (int cas = 1; cas <= T; cas++) {
 79             BigInteger L, R;
 80             L = cin.nextBigInteger();
 81             R = cin.nextBigInteger();
 82             BigInteger answer = solve(R).subtract(solve(L.subtract(BigInteger.ONE)));
 83             BigInteger Mod = answer;
 84             if (Mod.compareTo(BigInteger.ZERO) == 0) {
 85                 Mod = BigInteger.ZERO;
 86             }else {
 87                 Mod = Mod.mod(BigInteger.valueOf(9));
 88                 if (Mod.compareTo(BigInteger.ZERO) <= 0) Mod = Mod.add(BigInteger.valueOf(9));
 89             }
 90             if (Mod.equals(BigInteger.ZERO)) {
 91                 System.out.println("Error!");
 92             }else {
 93                 answer = answer.mod(Mod);
 94                 if (answer.compareTo(BigInteger.ZERO) < 0) answer = answer.add(Mod);
 95                 System.out.println(answer);
 96             }
 97         }
 98     }
 99
100 }

为什么java不能重载运算符呢!!!一个a = a.add(b) 写成 a.add(b)害的我差错查了1个小时啊！ T T

HDU 4933 Miaomiao's Function(数位DP + 高精度)