update

Task/Greatest-common-divisor/Java/greatest-common-divisor-4.java

@@ -1,6 +1,30 @@
-public static long gcd(long a, long b){
-   if(a == 0) return b;
-   if(b == 0) return a;
-   if(a > b) return gcd(b, a % b);
-   return gcd(a, b % a);
+public static long gcd(long u, long v){
+  long t, k;
+
+  if (v == 0) return u;
+
+  u = Math.abs(u);
+  v = Math.abs(v);
+  if (u < v){
+    t = u;
+    u = v;
+    v = t;
+  }
+
+  for(k = 1; (u & 1) == 0 && (v & 1) == 0; k <<= 1){
+    u >>= 1; v >>= 1;
+  }
+
+  t = (u & 1) != 0 ? -v : u;
+  while (t != 0){
+    while ((t & 1) == 0) t >>= 1;
+
+    if (t > 0)
+      u = t;
+    else
+      v = -t;
+
+    t = u - v;
+  }
+  return u * k;
 }