BASIC-12-十六进制转八进制

最后更新于:2022-04-01 09:41:23

问题描述 给定n个十六进制正整数,输出它们对应的八进制数。 输入格式 输入的第一行为一个正整数n (1<=n<=10)。 接下来n行,每行一个由0~9、大写字母A~F组成的字符串,表示要转换的十六进制正整数,每个十六进制数长度不超过100000。 输出格式 输出n行,每行为输入对应的八进制正整数。 【注意】 输入的十六进制数不会有前导0,比如012A。 输出的八进制数也不能有前导0。 样例输入   2   39   123ABC 样例输出   71   4435274 【提示】 先将十六进制数转换成二进制数,再由二进制数转换成八进制。    难点就是数值太大了,10w个F啊, 思路就是换成二进制再换成八进制,用java大数类一直超时,所以不能用大数方法 ### 先来超时的方法 ~~~ import java.math.BigInteger; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner input = new Scanner(System.in); int n = input.nextInt(); String[] arr = new String[n]; for (int i = 0; i < n; i++) { String temp = input.next(); BigInteger num = new BigInteger(temp,16); arr[i] = num.toString(8).toUpperCase(); } for (String string : arr) { System.out.println(string); } } } ~~~ ### 下面是正确的方法 ~~~ package com.day7; import java.util.Scanner; public class Main { //定义16进制需要的二进制码 static String[] hex = {"0000","0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"}; public static void main(String[] args) { Scanner input = new Scanner(System.in); int n = input.nextInt(); String[] arrs = new String[n]; for (int i = 0; i < n; i++) { arrs[i] = input.next(); } for (int i = 0; i < arrs.length; i++) { translateToOct(translateToBin(arrs[i])); } } //把得到的二进制串转换成八进制 private static void translateToOct(StringBuilder builder){ StringBuilder builder2 = new StringBuilder(); for (int i = 0; i < builder.length()-1; i = i+3) { switch (builder.substring(i, i+3)) { case "000": builder2.append("0"); break; case "001": builder2.append("1"); break; case "010": builder2.append("2"); break; case "011": builder2.append("3"); break; case "100": builder2.append("4"); break; case "101": builder2.append("5"); break; case "110": builder2.append("6"); break; case "111": builder2.append("7"); break; } } if (builder2.charAt(0) == '0') { builder2.deleteCharAt(0); } System.out.println(builder2.toString()); } //把输入的字符串变成二进制串 private static StringBuilder translateToBin(String str){ StringBuilder builder = new StringBuilder(); //转换后补0凑成3的倍数 if ((str.length()*4)%3 != 0) { if ((str.length()*4)%3 == 1) { builder.append("00"); }else { builder.append("0"); } } //接下来开始转换 for (int i = 0; i < str.length(); i++) { switch (str.charAt(i)) { case '0': builder.append(hex[0]); break; case '1': builder.append(hex[1]); break; case '2': builder.append(hex[2]); break; case '3': builder.append(hex[3]); break; case '4': builder.append(hex[4]); break; case '5': builder.append(hex[5]); break; case '6': builder.append(hex[6]); break; case '7': builder.append(hex[7]); break; case '8': builder.append(hex[8]); break; case '9': builder.append(hex[9]); break; case 'A': builder.append(hex[10]); break; case 'B': builder.append(hex[11]); break; case 'C': builder.append(hex[12]); break; case 'D': builder.append(hex[13]); break; case 'E': builder.append(hex[14]); break; case 'F': builder.append(hex[15]); break; } } return builder; } } ~~~
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