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")));
        }
        
    }
}