p405

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LeetCode p405 Convert a Number to Hexadecimal 题解

1.题目：

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”

题意：

输入一个数字输出它的16进制。

2.解题思路:

位运算 考虑全面（负数，0）
2进制-16进制

3.代码

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public class Solution {
    public String toHex(int num) {
        if (num == 0) return "0";
		StringBuilder sb = new StringBuilder();
		char[] c = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
		int a = 1+2+4+8;
		while (num != 0) {
			int i = num&a;
			num = num >>> 4; // 无符号右移，忽略符号位，空位都以0补齐
			sb.append(c[i]);
		}
		return sb.reverse().toString();
    }
}

4.一些总结：