题解 | 最大 FST 距离

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int count = scanner.nextInt();
        long max_a = Long.MIN_VALUE;
        long max_b = Long.MIN_VALUE;
        long min_a = Long.MAX_VALUE;
        long min_b = Long.MAX_VALUE;
        for (long i = 1; i <= count; i++) {
            long x = scanner.nextLong();
            max_a = Math.max(max_a, i * i - x * x);
            max_b = Math.max(max_b, i * i + x * x);
            min_a = Math.min(min_a, i * i - x * x);
            min_b = Math.min(min_b, i * i + x * x);

        }
        System.out.print(Math.max(Math.abs(max_a - min_a), Math.abs(max_b - min_b)));
    }

    private static long getFST(long[] arr, int i, int j) {
        long aa = Math.abs(arr[j] * arr[j] - arr[i] * arr[i]);
        long bb = Math.abs((j + 1)  * (j + 1) - (i + 1)  * (i + 1));
        // System.out.println("aa = " + aa + " " + bb);
        return aa + bb;
    }
}