Add Octal to Binary Conversion (TheAlgorithms#581)

Author: cyrixninja

src/conversions/octal_to_binary.rs

@@ -0,0 +1,61 @@
+// Author : cyrixninja
+// Octal to Binary Converter : Converts Octal to Binary
+// Wikipedia References  : 1. https://en.wikipedia.org/wiki/Octal
+//                         2. https://en.wikipedia.org/wiki/Binary_number
+
+fn octal_to_binary(octal_str: &str) -> Result<String, &'static str> {
+    let octal_str = octal_str.trim();
+
+    if octal_str.is_empty() {
+        return Err("Empty");
+    }
+
+    if !octal_str.chars().all(|c| c >= '0' && c <= '7') {
+        return Err("Non-octal Value");
+    }
+
+    // Convert octal to binary
+    let binary = octal_str
+        .chars()
+        .map(|c| match c {
+            '0' => "000",
+            '1' => "001",
+            '2' => "010",
+            '3' => "011",
+            '4' => "100",
+            '5' => "101",
+            '6' => "110",
+            '7' => "111",
+            _ => unreachable!(),
+        })
+        .collect::<String>();
+
+    Ok(binary)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_empty_string() {
+        let input = "";
+        let expected = Err("Empty");
+        assert_eq!(octal_to_binary(input), expected);
+    }
+
+    #[test]
+    fn test_invalid_octal() {
+        let input = "89";
+        let expected = Err("Non-octal Value");
+        assert_eq!(octal_to_binary(input), expected);
+    }
+
+    #[test]
+    fn test_valid_octal() {
+        let input = "123";
+        let expected = Ok("001010011".to_string()); 
+        assert_eq!(octal_to_binary(input), expected);
+    }
+    
+}