roman numbers converter

roman/roman.cpp

@@ -0,0 +1,61 @@
+#include <stdio.h>
+#include <iostream>
+#include <string.h>
+#include <string>
+#include <map>
+using namespace std;
+
+string HELLO_MESSAGE = "Please enter roman number: ";
+string RESULT        = "Result is";
+string ERROR         = "There were an error in the input.";
+
+string input;
+
+map<char,int>mapa;
+
+int roman_number(string S) {
+    int result = 0;
+
+    int last_digit = -1;
+    for(int i = 0, len = S.length();i < len; ++i) {
+        if(mapa[S[i]] == 0) return -1;
+
+        int digit_value = mapa[S[i]];
+        if(last_digit == -1) {
+            result = digit_value;
+            last_digit = digit_value;
+        } else if(digit_value <= last_digit) {
+            result += digit_value;
+            last_digit = digit_value;
+        } else { //IX CM
+            result -= last_digit;
+            result += (digit_value - last_digit);
+            last_digit = digit_value;
+        }
+    }
+
+    return result;
+}
+
+void init_map() {
+    mapa['I'] = 1;
+    mapa['V'] = 5;
+    mapa['X'] = 10;
+    mapa['L'] = 50;
+    mapa['C'] = 100;
+    mapa['D'] = 500;
+    mapa['M'] = 1000;
+}
+
+int main() {
+    cout << HELLO_MESSAGE;
+    cin >> input;
+    init_map();
+    int result = roman_number(input);
+    if(result == -1) {
+        cout << ERROR;
+    } else {
+        cout << RESULT << " " << result << endl;
+    }
+    return 0;
+}