Data commit

Task/Jacobi-symbol/Go/jacobi-symbol.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+    "fmt"
+    "log"
+    "math/big"
+)
+
+func jacobi(a, n uint64) int {
+    if n%2 == 0 {
+        log.Fatal("'n' must be a positive odd integer")
+    }
+    a %= n
+    result := 1
+    for a != 0 {
+        for a%2 == 0 {
+            a /= 2
+            nn := n % 8
+            if nn == 3 || nn == 5 {
+                result = -result
+            }
+        }
+        a, n = n, a
+        if a%4 == 3 && n%4 == 3 {
+            result = -result
+        }
+        a %= n
+    }
+    if n == 1 {
+        return result
+    }
+    return 0
+}
+
+func main() {
+    fmt.Println("Using hand-coded version:")
+    fmt.Println("n/a  0  1  2  3  4  5  6  7  8  9")
+    fmt.Println("---------------------------------")
+    for n := uint64(1); n <= 17; n += 2 {
+        fmt.Printf("%2d ", n)
+        for a := uint64(0); a <= 9; a++ {
+            fmt.Printf(" % d", jacobi(a, n))
+        }
+        fmt.Println()
+    }
+
+    ba, bn := new(big.Int), new(big.Int)
+    fmt.Println("\nUsing standard library function:")
+    fmt.Println("n/a  0  1  2  3  4  5  6  7  8  9")
+    fmt.Println("---------------------------------")
+    for n := uint64(1); n <= 17; n += 2 {
+        fmt.Printf("%2d ", n)
+        for a := uint64(0); a <= 9; a++ {
+            ba.SetUint64(a)
+            bn.SetUint64(n)
+            fmt.Printf(" % d", big.Jacobi(ba, bn))
+        }
+        fmt.Println()
+    }
+}