题解 | #进制转换#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String str = scan.nextLine();
        str = str.trim().substring(2);
        char[] chrs = str.toCharArray();
        HashMap<Character, Integer> CharacterToInteger = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            CharacterToInteger.put((char) ('0' + i), i);
        }
        for (int i = 10; i < 16; i++) {
            CharacterToInteger.put((char) ('A' + i - 10), i);
        }
        int ans = 0;
        for (int i = chrs.length - 1; i > -1; i--) { // 从数组的末尾开始往前遍历
            char chr = chrs[i]; // 获取当前位置上的字符
            int val = CharacterToInteger.get(chr); // 获取当前字符对应的数字
            ans += val * (int) Math.pow(16, chrs.length - 1 - i);
        }
        System.out.println(ans);
    }
}