Add solution 537

Author: vulgur

537_ComplexNumberMultiplication.swift

@@ -0,0 +1,16 @@
+class Solution {
+    func complexNumberMultiply(_ a: String, _ b: String) -> String {
+        let (a1, b1) = splitComplexNumber(a)
+        let (a2, b2) = splitComplexNumber(b)
+        let A = a1*a2 - b1*b2
+        let B = a1*b2 + a2*b1
+        return "\(A)+\(B)i"
+    }
+    
+    func splitComplexNumber(_ n: String) -> (Int, Int) {
+        let components = n.split(separator: "+")
+        let a = components[0]
+        let b = components[1]
+        return (Int(a)!, Int(b.prefix(b.count-1))!)
+    }
+}