RomanToDecimal

RomanToDecimal.cpp

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+#include <bits/stdc++.h> 
+using namespace std; 
+
+// This function returns value 
+// of a Roman symbol 
+int value(char r) 
+{ 
+    if (r == 'I') 
+        return 1; 
+    if (r == 'V') 
+        return 5; 
+    if (r == 'X') 
+        return 10; 
+    if (r == 'L') 
+        return 50; 
+    if (r == 'C') 
+        return 100; 
+    if (r == 'D') 
+        return 500; 
+    if (r == 'M') 
+        return 1000; 
+
+    return -1; 
+} 
+
+// Returns decimal value of 
+// roman numaral 
+int romanToDecimal(string& str) 
+{ 
+    // Initialize result 
+    int res = 0; 
+
+    // Traverse given input 
+    for (int i = 0; i < str.length(); i++) { 
+        // Getting value of symbol s[i] 
+        int s1 = value(str[i]); 
+
+        if (i + 1 < str.length()) { 
+            // Getting value of symbol s[i+1] 
+            int s2 = value(str[i + 1]); 
+
+            // Comparing both values 
+            if (s1 >= s2) { 
+                // Value of current symbol 
+                // is greater or equal to 
+                // the next symbol 
+                res = res + s1; 
+            } 
+            else { 
+                // Value of current symbol is 
+                // less than the next symbol 
+                res = res + s2 - s1; 
+                i++; 
+            } 
+        } 
+        else { 
+            res = res + s1; 
+        } 
+    } 
+    return res; 
+} 
+
+// Driver Program 
+int main() 
+{ 
+    // Considering inputs given are valid 
+    string str = "MCMIV"; 
+    cout << "Integer form of Roman Numeral is "
+         << romanToDecimal(str) << endl; 
+
+    return 0; 
+}