题解 | 数制转换

import java.util.LinkedList;
import java.util.Scanner;
import java.util.Stack;

// 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);

        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            String n = in.next();
            int b = in.nextInt();

            // 从右往左遍历字符串，转数值，将a进制的n转为10进制sum
            int res = 0;
            for (int index = 0; index < n.length(); index++) {
                int currentValue = getIntegerValue(n.charAt(index));
                res = res * a + currentValue;
            }

            // 处理结果为 0 的情况
            if (res == 0) {
                System.out.println(0);
                continue;
            }

            Stack<Character> stack = new Stack<>();
            while (res != 0) {//十进制转x进制
                stack.push(intTochar(res % b));
                res /= b;
            }

            while(!stack.isEmpty()){
                System.out.print(stack.pop());
            }
            System.out.println();
        }
    }

    public static int getIntegerValue(char c){
        if(c >= '0' && c<= '9'){
            return c-'0';
        }else if(c >= 'A' && c<= 'F'){
            return c - 'A' + 10;
        }else{
            return c - 'a' + 10;
        }
    }

    public static char intTochar(int num) {
    if (num > 9) {
        return (char)(num - 10 + 'A');
    } else {
        return (char)(num + '0');
    }
}
}