Ternary number

tdd_intro/homework/02_ternary_numbers/test.cpp

@@ -16,3 +16,32 @@ The last place in a ternary number is the 1's place. The second to last is the 3
 
 If your language provides a method in the standard library to perform the conversion, pretend it doesn't exist and implement it yourself.
 */
+
+int ConvertTernaryToDecimal(const std::string& ternaryNumber)
+{
+    int sum = 0;
+    long value = 1;
+    for(int i = ternaryNumber.length() - 1; i >= 0; --i)
+    {
+        sum += (ternaryNumber[i] - 48) * value;
+        value *= 3;
+    }
+
+    return sum;
+}
+
+
+TEST(TernaryNumber, OneConvertsToOneTest)
+{
+    EXPECT_EQ(1, ConvertTernaryToDecimal("1"));
+}
+
+TEST(TernaryNumber, ConvertValidTernaryNumberTest)
+{
+    EXPECT_EQ(5, ConvertTernaryToDecimal("012"));
+}
+
+TEST(TernaryNumber, ConvertAnotherValidTernaryNumberTest)
+{
+    EXPECT_EQ(302, ConvertTernaryToDecimal("102012"));
+}