add new solutions

solutions/0/q13/solution.go

@@ -0,0 +1,37 @@
+package q13
+
+func lookup(b byte) int {
+	switch b {
+	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
+}
+
+func romanToInt(s string) int {
+	num := 0
+	prev := 0
+	for i := range len(s) {
+		cur := lookup(s[i])
+		num += cur
+		if prev < cur {
+			num -= prev + prev
+		}
+		prev = cur
+	}
+	return num
+}
+
+var _ = romanToInt