LeetCode<Day1> toHex

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.

Note:

1. All letters in hexadecimal (a-f) must be in lowercase.
2. 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.
3. The given number is guaranteed to fit within the range of a 32-bit signed integer.
4. You must not use any method provided by the library which converts/formats the number to hex direct.

Answer:

public class toHex {
    public static void main(String[] args) {
        int num = -5;
        char[] map = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'}; /*定义一张图 分别放入16个代表十六进制中的数*/
        System.out.println(toHexMethod(num,map));

    }

    private static String  toHexMethod(int num,char[] map) {
        if(num == 0)
            return "0";
        String result = "";
        while(num != 0){
            result = map[(num & 15)] + result; 
            num = (num >>> 4);
        }
        return result;
        }
}

主要利用计算机二进制计算原理；

<<      :     左移运算符，num << 1,相当于num乘以2

>>      :     右移运算符，num >> 1,相当于num除以2

>>>    :     无符号右移，忽略符号位，空位都以0补齐

<<      :     左移运算符，num << 1,相当于num乘以2

>>      :     右移运算符，num >> 1,相当于num除以2

>>>    :     无符号右移，忽略符号位，空位都以0补齐