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"

将一个十进制的数转换成十六进制的数

class Solution {
public:
    string toHex(int num) {
        int count = 0;
        if(!num) return "0";
        string result;
         //此处可以跳过开头的0
        while (num !=  0 && count < 8)
        {
            int temp = num & 0xf;
            if (temp<10)    result.push_back('0'+ temp);
            else result.push_back('a'+temp-10);
            num = num >> 4;
            count++;
        }
        reverse(result.begin(),result.end());
        return result;
    }
};