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  • Leetcode: Convert a Number to Hexadecimal

    Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.
    
    Note:
    
    All letters in hexadecimal (a-f) must be in lowercase.
    The hexadecimal string must not contain extra leading 0s. If the number is zero, it is represented by a single zero character '0'; otherwise, the first character in the hexadecimal string will not be the zero character.
    The given number is guaranteed to fit within the range of a 32-bit signed integer.
    You must not use any method provided by the library which converts/formats the number to hex directly.
    Example 1:
    
    Input:
    26
    
    Output:
    "1a"
    Example 2:
    
    Input:
    -1
    
    Output:
    "ffffffff"

    记住要delete begining 0

     1 public class Solution {
     2     public String toHex(int num) {
     3         StringBuffer res = new StringBuffer();
     4         String[] charMap = new String[]{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
     5         for (int i=0; i<8; i++) {
     6             int number = num & (0b1111);
     7             num = num >>> 4;
     8             res.insert(0, charMap[number]);
     9         }
    10         while (res.charAt(0)=='0' && res.length()>1) res.deleteCharAt(0);
    11         return res.toString();
    12     }
    13 }

    要记住单独处理 num == 0的情况

     1 public class Solution {
     2     public String toHex(int num) {
     3         if (num == 0) return "0";
     4         StringBuffer res = new StringBuffer();
     5         String[] charMap = new String[]{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
     6         while (num != 0) {
     7             int number = num & (0b1111);
     8             num = num >>> 4;
     9             res.insert(0, charMap[number]);
    10         }
    11         return res.toString();
    12     }
    13 }
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  • 原文地址:https://www.cnblogs.com/EdwardLiu/p/6124957.html
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