Fix integer overflow in LCM algorithm

Author: egorzhdan

GCD/GCD.playground/Contents.swift

@@ -32,7 +32,7 @@ func gcd(m: Int, _ n: Int) -> Int {
 */
 
 func lcm(_ m: Int, _ n: Int) -> Int {
-  return m*n / gcd(m, n)
+  return m / gcd(m, n) * n // we divide before multiplying to avoid integer overflow
 }
 
 gcd(52, 39)       // 13

GCD/GCD.swift

@@ -30,5 +30,5 @@ func gcd(_ a: Int, _ b: Int) -> Int {
   Returns the least common multiple of two numbers.
 */
 func lcm(_ m: Int, _ n: Int) -> Int {
-  return m*n / gcd(m, n)
+  return m / gcd(m, n) * n
 }

GCD/README.markdown

@@ -102,7 +102,7 @@ In code:
 
 ```swift
 func lcm(_ m: Int, _ n: Int) -> Int {
-  return m*n / gcd(m, n)
+  return m / gcd(m, n) * n
 }
 ```