题解 | #进制转换#

import java.util.Scanner;

// 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);
        String num16 = scanner.next();
        String[] array =new String[num16.length()];
        for (int i = 0; i < array.length; i++) {
            array[i]= String.valueOf(num16.charAt(i));
        }
        int sum = 0;
        for (int i = 2; i < array.length; i++) {
            if (array[i].equalsIgnoreCase("a")){
                sum= (int) (sum+10*Math.pow(16.,array.length-i-1));
            }
            else if (array[i].equalsIgnoreCase("b")){
                sum= (int) (sum+11*Math.pow(16.,array.length-i-1));
            }
            else if (array[i].equalsIgnoreCase("c")){
                sum= (int) (sum+12*Math.pow(16.,array.length-i-1));
            }
            else if (array[i].equalsIgnoreCase("d")){
                sum= (int) (sum+13*Math.pow(16.,array.length-i-1));
            }
            else if (array[i].equalsIgnoreCase("e")){
                sum= (int) (sum+14*Math.pow(16.,array.length-i-1));
            }
            else if (array[i].equalsIgnoreCase("f")){
                sum= (int) (sum+15*Math.pow(16.,array.length-i-1));
            }
            else  {
                sum= (int) (sum+Integer.parseInt(array[i])*Math.pow(16.,array.length-i-1));
            }

        }
        System.out.println(sum);
    }
}