405. 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:

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       Input:
       
       
26
       
       

       
       
Output:
       
       
"1a"
      
      
      
      

       
       
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Example 2:

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       Input:
       
       
-1
       
       

       
       
Output:
       
       
"ffffffff"
      
      
      
      

       
       
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       class Solution {
       
       
    public String toHex(int num) {
       
       
        if(num < 10 && num >= 0) 
       
       
            return Integer.toString(num);  
       
       
        char[] hex = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};  
       
       
        StringBuilder sb = new StringBuilder();  
       
       
        for(int i = 0;i < 8 && num != 0;i++) {  
       
       
            sb.insert(0,hex[num & 15]);  
       
       
            num = num>>4;  
       
       
        }  
       
       
        return
      
      
      
      

       
       
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