Add problem 13.

1 files changed, 54 insertions, 0 deletions

diff --git a/cpp/13.cpp b/cpp/13.cpp
new file mode 100644
index 0000000..486c01b
--- /dev/null
+++ b/cpp/13.cpp
@@ -0,0 +1,54 @@
+#include <string>
+
+using std::string;
+
+int romanDigitNumber(char romanDigit)
+{
+    switch (romanDigit)
+    {
+    case 'I':
+        return 1;
+    case 'V':
+        return 5;
+    case 'X':
+        return 10;
+    case 'L':
+        return 50;
+    case 'C':
+        return 100;
+    case 'D':
+        return 500;
+    case 'M':
+        return 1000;
+    };
+    return 0;
+}
+
+class Solution
+{
+public:
+    int romanToInt(string s)
+    {
+        int result = 0;
+
+        int count = s.size();
+
+        for (int i = 0; i < count; i++)
+        {
+            const char c = s[i];
+            int num = romanDigitNumber(c);
+            if (i < count - 1)
+            {
+                const char next = s[i + 1];
+                if ((c == 'I' && (next == 'V' || next == 'X')) || (c == 'X' && (next == 'L' || next == 'C')) || (c == 'C') && (next == 'D' || next == 'M'))
+                {
+                    num = -num;
+                }
+            }
+
+            result += num;
+        }
+
+        return result;
+    }
+};