add kata

5kyu/count-ip-addresses/solution.ts

@@ -0,0 +1,17 @@
+/**
+ * Regards an IP address as a number with 4 digits.
+ * Each digit can be between 0 and 255.
+ * The result of this function is the total number of possible IPs 'lower' than the given IP.
+ */
+const ipToNum = (ip: string): number => {
+  const digits = ip.split('.').map(Number) as [number, number, number, number];
+  console.log(digits);
+  if(digits.length !== 4) {
+    throw new Error('Invalid IP address');
+  }
+  return digits.reduce((sum, digit) => sum * 256 + digit, 0);
+}
+
+export function ipsBetween(start: string, end: string): number {
+  return ipToNum(end) - ipToNum(start);
+}