Heron and His Triangle 2017 沈阳区域赛

A triangle is a Heron’s triangle if it satisfies that the side lengths of it are consecutive integers t−1, t, t+ 1 and thatits area is an integer. Now, for given n you need to find a Heron’s triangle associated with the smallest t bigger 
than or equal to n.

InputThe input contains multiple test cases. The first line of a multiple input is an integer T (1 ≤ T ≤ 30000) followedby T lines. Each line contains an integer N (1 ≤ N ≤ 10^30). 
OutputFor each test case, output the smallest t in a line. If the Heron’s triangle required does not exist, output -1.Sample Input

4
1
2
3
4

Sample Output

4
4
4
4

题目是求大于等于的最小t使t，t-1，t+1构成的三角形的面积是一个整数
然后就是打表找规律。。
做题的时候一直在想用推出来的公式打表，结果最好看题解竟然是一个大数找规律。唉。
因为是大数所以用java做的。

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

public class Main
{
    public static void main(String[] args)
    {
        Scanner cin=new Scanner(new BufferedInputStream(System.in));
        BigInteger res[] = new BigInteger[100];
        res[0] = BigInteger.valueOf(4L);
        res[1] = BigInteger.valueOf(14L);
        for (int i = 2;i < 100;i++) {
            res[i] = res[i-1].multiply(new BigInteger("4")).subtract(res[i-2]);
        }
        while (cin.hasNext()) {
            int t = cin.nextInt();
            for (int ca = 1;ca <= t;ca++) {
                BigInteger n = cin.nextBigInteger();
                int i = 0;
                for (i = 0;i < 100;i++) {
                    if (n.compareTo(res[i]) != 1) break;
                }
                System.out.println(res[i]);
            }
        }
        cin.close();
    }
}