Add Hexadecimal to Binary Converter (#585)

Author: cyrixninja

src/conversions/hexadecimal_to_binary.rs

@@ -0,0 +1,67 @@
+// Author : cyrixninja
+// Hexadecimal to Binary Converter : Converts Hexadecimal to Binary
+// Wikipedia References  : 1. https://en.wikipedia.org/wiki/Hexadecimal
+//                         2. https://en.wikipedia.org/wiki/Binary_number
+// Other References for Testing : https://www.rapidtables.com/convert/number/hex-to-binary.html
+
+fn hexadecimal_to_binary(hex_str: &str) -> Result<String, String> {
+    let hex_chars = hex_str.chars().collect::<Vec<char>>();
+    let mut binary = String::new();
+
+    for c in hex_chars {
+        let bin_rep = match c {
+            '0' => "0000",
+            '1' => "0001",
+            '2' => "0010",
+            '3' => "0011",
+            '4' => "0100",
+            '5' => "0101",
+            '6' => "0110",
+            '7' => "0111",
+            '8' => "1000",
+            '9' => "1001",
+            'a' | 'A' => "1010",
+            'b' | 'B' => "1011",
+            'c' | 'C' => "1100",
+            'd' | 'D' => "1101",
+            'e' | 'E' => "1110",
+            'f' | 'F' => "1111",
+            _ => return Err("Invalid".to_string()),
+        };
+        binary.push_str(bin_rep);
+    }
+
+    Ok(binary)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_empty_string() {
+        let input = "";
+        let expected = Ok("".to_string());
+        assert_eq!(hexadecimal_to_binary(input), expected);
+    }
+
+    #[test]
+    fn test_hexadecimal() {
+        let input = "1a2";
+        let expected = Ok("000110100010".to_string());
+        assert_eq!(hexadecimal_to_binary(input), expected);
+    }
+    #[test]
+    fn test_hexadecimal2() {
+        let input = "1b3";
+        let expected = Ok("000110110011".to_string());
+        assert_eq!(hexadecimal_to_binary(input), expected);
+    }
+
+    #[test]
+    fn test_invalid_hexadecimal() {
+        let input = "1g3";
+        let expected = Err("Invalid".to_string());
+        assert_eq!(hexadecimal_to_binary(input), expected);
+    }
+}