JAVA BigDecimal 运用

exercise

package xrz385;
import java.util.*;
import java.io.*;
import java.math.BigDecimal;

public class f {
    public static int n;
    public static long[] X, H;

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        n = s.nextInt();
        X = new long[n + 10];
        H = new long[n + 10];
        BigDecimal ans = new BigDecimal("-1e100"); // 初始化为极小值

        for (int i = 1; i <= n; i++) {
            X[i] = s.nextLong();
            H[i] = s.nextLong();
        }

        for (int i = 2; i <= n; i++) {
            // 计算斜率 k = (H[i] - H[i-1]) / (X[i] - X[i-1])
            BigDecimal hi = BigDecimal.valueOf(H[i]);
            BigDecimal hi1 = BigDecimal.valueOf(H[i - 1]);
            BigDecimal xi = BigDecimal.valueOf(X[i]);
            BigDecimal xi1 = BigDecimal.valueOf(X[i - 1]);

            BigDecimal slope = hi.subtract(hi1).divide(xi.subtract(xi1), 20, BigDecimal.ROUND_HALF_UP);

            // 计算 y = H[i] - k * X[i]
            BigDecimal y = hi.subtract(slope.multiply(xi));

            // 更新答案
            ans = ans.max(y);
        }

        // 如果答案大于等于 0，输出结果；否则输出 -1
        if (ans.compareTo(BigDecimal.valueOf(0)) >= 0) {
            System.out.printf("%.20f", ans);
        } else {
            System.out.print(-1);
        }
    }
}