Added javascript solution for 13. Roman to Integer

Author: berkslv

javascript/13-Roman-to-Integer.js

@@ -0,0 +1,65 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var romanToInt = function (s) {
+    let romans = {
+        I: 1,
+        V: 5,
+        X: 10,
+        L: 50,
+        C: 100,
+        D: 500,
+        M: 1000,
+    };
+
+    let arr = s.split("");
+
+    let sum = 0;
+
+    for (let i = arr.length - 1; i >= 0; i--) {
+        // IV : 4
+        if (romans[arr[i]] === romans["V"]) {
+            if (romans[arr[i - 1]] === romans["I"]) {
+                sum -= 1 * 2;
+            }
+        }
+        // IX : 4
+        if (romans[arr[i]] === romans["X"]) {
+            if (romans[arr[i - 1]] === romans["I"]) {
+                sum -= 1 * 2;
+            }
+        }
+        // XL : 40
+        if (romans[arr[i]] === romans["L"]) {
+            if (romans[arr[i - 1]] === romans["X"]) {
+                sum -= 10 * 2;
+            }
+        }
+        // XC : 90
+        if (romans[arr[i]] === romans["C"]) {
+            if (romans[arr[i - 1]] === romans["X"]) {
+                sum -= 10 * 2;
+            }
+        }
+        // CD : 400
+        if (romans[arr[i]] === romans["D"]) {
+            if (romans[arr[i - 1]] === romans["C"]) {
+                sum -= 100 * 2;
+            }
+        }
+        // CM : 900
+        if (romans[arr[i]] === romans["M"]) {
+            if (romans[arr[i - 1]] === romans["C"]) {
+                sum -= 100 * 2;
+            }
+        }
+
+        sum += romans[arr[i]];
+    }
+
+    return sum;
+};
+
+// Runtime: 148 ms, faster than 80.16% of JavaScript online submissions for Roman to Integer.
+// Memory Usage: 47.5 MB, less than 18.15% of JavaScript online submissions for Roman to Integer.