LeetCode405 Convert a Number to Hexadecimal

题目要求

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”

public class leetcode405 {

public String toHex(int num) {

StringBuffer sb = new StringBuffer();
//创建数组用于存储数据
String[] arr = new String[16];
for(int i = 0; i < 16; i++) {
if(i < 10) arr[i] = i + "";
else arr[i] =(char)('a' + i-10) + "";
}
return parsetoHex(num, arr, sb);
}

public String parsetoHex(int num, String[] arr, StringBuffer sb) {

if(num == 0) return "0";
else if(num > 0) {
while(num > 0) {
int temp = num % 16;
sb.append(arr[temp]);
num /= 16;
}
return sb.reverse().toString();
}
else if(num < 0) {
int numx = - num - 1;
while(numx > 0) {
int temp = numx % 16;
sb.append(arr[15 - temp]);
numx /= 16;
}
while(sb.length() < 8) {
sb.append("f");
}
return sb.reverse().toString();
}
return null;
}
}