Heron and His Triangle HDU

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.

Input

The 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).

Output

For 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

打表发现数列规律 f[n]=4*f[n-1]-f[n-2]

大数写JAVA！

package a;
import java.util.Scanner;
import java.math.BigInteger;
public class A {
	public static void main(String[] args)
	{
		BigInteger[] num=new BigInteger[105];
		num[0]=BigInteger.valueOf(4);
		num[1]=BigInteger.valueOf(14);
		for(int i=2;i<100;i++)
		{
			num[i]=num[i-1].multiply(num[0]);
			num[i]=num[i].subtract(num[i-2]);
		}
		Scanner cin=new Scanner(System.in);
		int t=cin.nextInt();
		while(t--!=0)
		{
			BigInteger n=cin.nextBigInteger();
			for(int i=0;i<99;i++)
			{
				if(num[i].compareTo(n)!=-1)
				{
					System.out.println(num[i]);
					break;
				}
			}
		}
	}
}