多校-HDU 5351 MZL's Border 数学规律

f[1] = 'b', f[2] = 'a', f[i] = f[i - 1] + f[i - 2]

斐波那契数列的字符串，给你n和m，前m位中，最长的前缀等于后缀的长度是多少。1≤n≤1000, 1≤m≤length(f[n])

规律题，虽然我不知道为什么。

 import java.io.*;
 import java.util.*;
 import java.math.*;
 public class Main{
     //Scanner cin = Scanner(System.in);
     static BigInteger f[] = new BigInteger[1005];
     public static void main(String[] args){
         f[1] = new BigInteger("1");
         f[2] = new BigInteger("2");
         for(int i = 3; i <= 1001; i++){
             //f[i].valueOf(f[i - 1);
             //f[i] = f[i - 1];
             f[i] = f[i - 1].add(f[i - 2]);
             //f[i].add(f[i - 2]);
             //System.out.println(f[i]);
         }
         Scanner cin = new Scanner(System.in);
         int T = cin.nextInt();
         int n;
         BigInteger m;
         for(int cas = 1; cas <= T; cas++){
             n = cin.nextInt();
             m = cin.nextBigInteger();
             BigInteger mm = m.add(new BigInteger("1"));
             int p = 0;
             for(int i = 1; i <= 1001; i++){
                 if(f[i].compareTo(mm) > 0){
                     p = i;
                     break;
                 }
             }
             BigInteger ans = m.subtract(f[p - 2]);
             System.out.println(ans.mod(new BigInteger("258280327")));
         }

     }
 }