Data commit

Task/Pells-equation/Julia/pells-equation.julia

@@ -0,0 +1,22 @@
+function pell(n)
+    x = BigInt(floor(sqrt(n)))
+    y, z, r = x, BigInt(1), x << 1
+    e1, e2, f1, f2 = BigInt(1), BigInt(0), BigInt(0), BigInt(1)
+    while true
+        y = r * z - y
+        z = div(n - y * y, z)
+        r = div(x + y, z)
+        e1, e2 = e2, e2 * r + e1
+        f1, f2 = f2, f2 * r + f1
+        a, b = f2, e2
+        b, a = a, a * x + b
+        if a * a - n * b * b == 1
+            return a, b
+        end
+    end
+end
+
+for target in BigInt[61, 109, 181, 277]
+    x, y = pell(target)
+    println("x\u00b2 - $target", "y\u00b2 = 1 for x = $x and y = $y")
+end