题解 | 进制转换

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 in = new Scanner(System.in);
        String s = in.nextLine();
        int decimal = 0;
        int length = s.length();
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            int digit=0;
            if (c >= '0' && c <= '9') {
                digit = c - '0';
            } else if (c >= 'a' && c <= 'f') {
                digit = 10 + (c - 'a');
            } else if (c >= 'A' && c <= 'F') {
                digit = 10 + (c - 'A');
            } 
            decimal = decimal * 16 + digit;
        }
        System.out.println(decimal);
    }
}