LeetCode -- Convert a Number to Hexadecimal

题目描述：


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"


10进制转16进制。
不断取余数即可，需要考虑到负数和0的情况。




实现代码：

public class Solution {
    public string ToHex(int num) {
        if(num == 0){
    		return "0";
    	}
        var n = PositiveNum(num);
    	var ret = "";
    	
    	while(n > 0){
    		var r = n%16;
    		if(r < 10){
    			ret = r+ret;
    		}
    		else {
    			var x = (char)((int)'a' +r-10);
    			//Console.WriteLine(r+","+x);
    			ret = x + ret;
    		}
    		n = n/16;
    		//Console.WriteLine(ret + ","+n);
    	}
    	
    	//ret = n+ret;
    	
    	return ret;
}


private long PositiveNum(int i){
	if(i < 0){
		return (long)Math.Pow(2,32) + i;
	}
	return i;
}
    
}