題目連結

題意：給定一個數n$n$，判斷n$n$和n(n−1)/2$n(n-1)/2$是否是完全平方數

思路：
使用Java的BigInteger，對這兩個數開方以後，再對得到的數進行平方，判斷是否相等。

所以套上一個大數開方的模板即可。

程式碼：

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Scanner;

public
 
 class Main {
      static Scanner cin;

      public static boolean check(BigInteger now){
            if (now.compareTo(BigInteger.ZERO) == 0 || now.compareTo(BigInteger.ONE) == 0) return true;
            if (now.mod(BigInteger.valueOf(3)).compareTo(BigInteger.valueOf(2)) == 0) return false;


            String s = now.toString();
            if
 
(s.length()%2==0) s = s.substring(0,s.length()/2+1);
            else                s = s.substring(0,(1+s.length())/2);

            BigInteger res = BigInteger.ZERO;
            BigInteger m = new BigInteger(s);
            BigInteger two = new BigInteger("2");
            if(s == "1") res = BigInteger.ONE;
            else
 
{
                while(now.compareTo(m.multiply(m)) < 0){
                     m = (m.add(now.divide(m))).divide(two);
                }
                res = m;
            }

            if (res.multiply(res).compareTo(now) == 0) return true;
            return false;
      }

      public static void main(String argv[]){
         cin = new Scanner(System.in);
         BigInteger n, m;
         int T = cin.nextInt();
         while (T > 0) {
             T--;
             n = cin.nextBigInteger();
             m = n.multiply(n.subtract(BigInteger.ONE)).divide(BigInteger.valueOf(2));

             boolean flag1 = check(n), flag2 = check(m);
             if (flag1 && flag2) System.out.println("Arena of Valor");
             else if (flag1)     System.out.println("Hearth Stone");
             else if (flag2)     System.out.println("Clash Royale");
             else                System.out.println("League of Legends");
         }
      }
}