Added task 13.

Author: javadev

src/main/kotlin/g0001_0100/s0013_roman_to_integer/Solution.kt

@@ -0,0 +1,36 @@
+package g0001_0100.s0013_roman_to_integer
+
+class Solution {
+    fun romanToInt(s: String): Int {
+        var x = 0
+        var y: Char
+        for (i in s.indices) {
+            y = s[i]
+            when (y) {
+                'I' -> x = getX(s, x, i, 1, 'V', 'X')
+                'V' -> x += 5
+                'X' -> x = getX(s, x, i, 10, 'L', 'C')
+                'L' -> x += 50
+                'C' -> x = getX(s, x, i, 100, 'D', 'M')
+                'D' -> x += 500
+                'M' -> x += 1000
+                else -> {}
+            }
+        }
+        return x
+    }
+
+    private fun getX(s: String, x: Int, i: Int, i2: Int, v: Char, x2: Char): Int {
+        var localX = x
+        if (i + 1 == s.length) {
+            localX += i2
+        } else if (s[i + 1] == v) {
+            localX -= i2
+        } else if (s[i + 1] == x2) {
+            localX -= i2
+        } else {
+            localX += i2
+        }
+        return localX
+    }
+}

src/test/kotlin/g0001_0100/s0013_roman_to_integer/SolutionTest.kt

@@ -0,0 +1,19 @@
+package g0001_0100.s0013_roman_to_integer
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+
+import org.junit.Test
+
+class SolutionTest {
+    @Test
+    fun romanToInt() {
+        val solution = Solution()
+        assertThat(solution.romanToInt("III"), equalTo(3))
+        assertThat(solution.romanToInt("IV"), equalTo(4))
+        assertThat(solution.romanToInt("IX"), equalTo(9))
+        assertThat(solution.romanToInt("LVIII"), equalTo(58))
+        assertThat(solution.romanToInt("MCMXCIV"), equalTo(1994))
+    }
+
+}