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”

题解：这题就是简单的进制转换，十进制到十六进制直接除16再逆转顺序就ok。
所以解题思路相对比较简单。

class Solution {    public:        string toHex(int num) {            vector<int> vec;            string str="";            long long temp=0;            if(num==0){//应对为0的情况                vec.push_back(0);            }            if(num>0){                temp=num;            }            if(num<0){//应对为负数的情况                temp=pow(2,32)+num;            }            while(temp!=0){                long long a=temp%16;                temp=temp/16;                vec.push_back(a);            }            for(int i=0;i<vec.size();i++){                if(vec[i]>=10){                    char s=vec[i]-10+'a';                }                else{                    char s=vec[i]+'0';                }                str=s+str;            }            return str;    }};