leetcode-convert-a-number-hexadecimal

题目大意

　　https://leetcode.com/problems/convert-a-number-to-hexadecimal/

　　将一32位整数转成补码表示

题目分析

　　其实就是把整数在计算机内的真实存储形式表示出来，注意题目要求结果的前面不允许有引导‘0’。（正数转换成相应的负数（反过来也一样）的方式都是：所有位取反然后加1，0要单独考虑）

代码

public class Solution {
    private static char[] symbol = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    
    public String toHex(int num) {
        if (num == 0) {
            return "0";
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 8; i++) {
            sb.append(symbol[num & 15]);
            num >>= 4;
        }
        String tmp = sb.reverse().toString();
        StringBuilder sb2 = new StringBuilder();
        boolean found = false;
        for (int i = 0; i < 8; i++) {
            if (tmp.charAt(i) != '0') {
                found = true;
            }
            if (found) {
                sb2.append(tmp.charAt(i));
            }
        }
        return sb2.toString();
    }
}