Convert a Number to Hexadecimal

最新推荐文章于 2024-01-18 20:49:56 发布

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最新推荐文章于 2024-01-18 20:49:56 发布

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分类专栏：算法文章标签： C++ leetcode 程序设计

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本文介绍了一种将整数转换为十六进制字符串的方法，包括处理负数时使用二进制补码的方式。提供了详细的算法步骤及示例。

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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"

INT的取值范围是（-2^31,2^31-1)；

对于负数，除首位的符号位，后面的值为2^31+num

class Solution {
   
public:
    string toHex(int num) {
        if(num==0)
        return "0";
        if(num==INT_MIN)//(-2^31)
        return "80000000";
        long long a;
        if(num>0) a=num;
        else a=(1<<31)+num;//除了符号位之后的，注意对INT_MIN要事先处理
        string s;
         char c;
        while(a)
        {
           
            int i=a%16;
            if(i>9)
            c='a'+(i-10);
            else 
            c='0'+i;
            s=c+s;
            a/=16;
        }
        //根据符号不同，处理最后一位
        if(num<0)
        {
          int i=s[0]-'0'+(1<<3);
          if(i>9)
          s[0]='a'+(i-10);
          else
          s[0]='0'+i;
		}
        return s;
        
    }
};