蓝桥杯 基础练习 十六进制转八进制

问题描述

Java 代码实现

方案一：使用 BigInteger 类直接转换。

import java.math.BigInteger;
import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        int n = in.nextInt();
        for (int i = 0; i < n; ++i) {
            String s = in.next();
            BigInteger temp = new BigInteger(s, 16);
            System.out.println(temp.toString(8));
        }

        in.close();
    }
}

方案二：由十六进制先转换为二进制然后转换为八进制。

import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        int n = in.nextInt();
        for (int i = 0; i < n; ++i) {
            String s = in.next();
            System.out.println(binToOct(henToBin(s)));
        }

        in.close();
    }
    // 十六进制转二进制
    public static StringBuilder henToBin(String s) {
        Map<Character, String> map = new HashMap<Character, String>();
        map.put('0', "0000");map.put('1', "0001");map.put('2', "0010");map.put('3', "0011");
        map.put('4', "0100");map.put('5', "0101");map.put('6', "0110");map.put('7', "0111");
        map.put('8', "1000");map.put('9', "1001");map.put('A', "1010");map.put('B', "1011");
        map.put('C', "1100");map.put('D', "1101");map.put('E', "1110");map.put('F', "1111");
        StringBuilder sb = new StringBuilder();
        final int len = s.length();
        for (int i = 0; i < len; ++i) {
            sb.append(map.get(s.charAt(i)));
        }
        return sb;
    }
    // 二进制转八进制
    public static StringBuilder binToOct(StringBuilder s) {
        Map<String, Character> map = new HashMap<String, Character>();
        map.put("000", '0');map.put("001", '1');map.put("010", '2');map.put("011", '3');
        map.put("100", '4');map.put("101", '5');map.put("110", '6');map.put("111", '7');
        StringBuilder sb = new StringBuilder();
        int len = s.length();
        // 长度变为3的倍数，便于转换
        int temp = len % 3;
        if (temp != 0) {
            s.insert(0, temp==1?"00":"0");
            len = s.length();
        }
        // 开始转换
        for (int i = 0; i < len; i+=3) {
            sb.append(map.get(s.substring(i, i+3)));
        }
        // 去除前面的0
        len = sb.length();
        for (int i = 0; i < len; ++i) {
            if (sb.charAt(i) == '0') {
                sb.deleteCharAt(i);
            } else {
                break;
            }
        }
        return sb;
    }
}