Bit Manipulation: 405. Convert a Number to Hexadecimal

Author: shaikrasheed99

README.md

@@ -48,6 +48,7 @@
   * [338](https://leetcode.com/problems/counting-bits/). Counting Bits - [code](src/bit_manipulation/easy/CountingBits.java)
   * [137](https://leetcode.com/problems/single-number-ii/). Single Number II - [code](src/bit_manipulation/easy/OneSingleNumberInGroupOfThreeNumbers.java)
   * [260](https://leetcode.com/problems/single-number-iii/). Single Number III - [code](src/bit_manipulation/easy/TwoSingleNumbers.java)
+  * [405](https://leetcode.com/problems/convert-a-number-to-hexadecimal/). Convert a Number to Hexadecimal - [code](src/bit_manipulation/easy/ConvertANumberToHexadecimal.java)
   * [Gfg](https://practice.geeksforgeeks.org/problems/check-whether-k-th-bit-is-set-or-not-1587115620/1). Check whether K-th bit is set or not - [code](src/bit_manipulation/easy/CheckKthBitIsSet.java)
   * [Gfg](https://practice.geeksforgeeks.org/problems/odd-or-even3618/1). Odd or Even - [code](src/bit_manipulation/easy/OddOrEven.java)
   * [Gfg](https://practice.geeksforgeeks.org/problems/set-kth-bit3724/1). Set kth bit - [code](src/bit_manipulation/easy/SetKthBit.java)

src/bit_manipulation/easy/ConvertANumberToHexadecimal.java

@@ -0,0 +1,77 @@
+package bit_manipulation.easy;
+
+/***
+ * Problem 405 in Leetcode: https://leetcode.com/problems/convert-a-number-to-hexadecimal/
+ *
+ * Given an integer num, return a string representing its hexadecimal representation.
+ * For negative integers, two’s complement method is used.
+ * All the letters in the answer string should be lowercase characters
+ * and there should not be any leading zeros in the answer except for the zero itself.
+ *
+ * Note: You are not allowed to use any built-in library method to directly solve this problem.
+ *
+ * Example 1:
+ * Input: num = 26
+ * Output: "1a"
+ *
+ * Example 2:
+ * Input: num = -1
+ * Output: "ffffffff"
+ */
+
+public class ConvertANumberToHexadecimal {
+    private static final char[] chars = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+    public static void main(String[] args) {
+        int num = -1;
+
+        System.out.println("Brute Force: " + convertIntoHexadecimalBruteForce(num));
+        System.out.println("Bitwise: " + convertIntoHexadecimalBitwise(num));
+    }
+
+    private static String convertIntoHexadecimalBruteForce(int num) {
+        if (num == 0) {
+            return "0";
+        }
+
+        boolean isNegative = num < 0;
+
+        num = isNegative ? (num + 1) * -1 : num;
+
+        StringBuilder sb = new StringBuilder();
+
+        while (num > 0) {
+            int r = num % 16;
+            if (isNegative) {
+                r = 15 - r;
+            }
+            char c = (char) (r < 10 ? r + '0' : r - 10 + 'a');
+            sb.append(c);
+            num /= 16;
+        }
+
+        if (isNegative) {
+            while (sb.length() < 8) {
+                sb.append('f');
+            }
+        }
+
+        return sb.reverse().toString();
+    }
+
+    private static String convertIntoHexadecimalBitwise(int num) {
+        if (num == 0) {
+            return "0";
+        }
+
+        StringBuilder result = new StringBuilder();
+
+        while (num != 0) {
+            int mask = 15;
+            result.append(chars[(num & mask)]);
+            num >>>= 4;
+        }
+
+        return result.reverse().toString();
+    }
+}