【LeetCode】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:

Input:
26

Output:
“1a”
Example 2:

Input:
-1

Output:
“ffffffff”

class Solution {
public:
    string toHex(int num) {
        if(num==0)return "0";
        char hex[] = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'}; 
        string ans;
        for(int i=0;i<8&&num;i++){
            ans=hex[num&15]+ans;
            num>>=4;
        }
        return ans;
    }
};