mcichecki · June 23, 2018 11:03 · Jun 23, 2018
diff --git a/modInverse.swift b/modInverse.swift
@@ -0,0 +1,19 @@
+/*
+given a and m, function finds x for a * x = 1 (mod m)
+
+24 * x = 1 (mod 5)
+24 = x*exp(-1) (mod 5)
+x = 4
+
+modInverse(a: 24, m: 5) returns optional(4)
+*/
+
+func modInverse(a: Int, m: Int) -> Int? {
+	let tmp = a % m
+    for i in 1..<m {
+      if (tmp * i % m == 1) {
+        return i;
+      }
+    }
+  return nil    
+}