feat(tricks): coprimes list

Signed-off-by: Pouyan Heyratpour <[email protected]>

tricks/mathx/arithmetic.go

@@ -58,6 +58,24 @@ func PrimeFactors(n int) []int {
 	return ff[:len(ff):len(ff)]
 }
 
+// CoprimesInRange returns list of all natural numbers in closed range [from, to]
+// which are coprime to the given number (n)
+func CoprimesInRange(n, from, to int) []int {
+	cpp := make([]int, 0, 10)
+	for i := from; i <= to; i++ {
+		if Gcd(n, i) == 1 {
+			cpp = append(cpp, i)
+		}
+	}
+
+	return cpp[:len(cpp):len(cpp)]
+}
+
+// MinorCoprimes returns list of all natural numbers which are less than the given number (n) and coprime to it
+func MinorCoprimes(n int) []int {
+	return CoprimesInRange(n, 1, n-1)
+}
+
 // NextPrime returns next prime number greater than the given number (n)
 func NextPrime(n int) int {
 	if n < 1 {

tricks/mathx/arithmetic_test.go

@@ -162,6 +162,16 @@ func TestPrimes(t *testing.T) {
 	assert.Equal(t, []int{}, mathx.PrimeFactors(-127))
 }
 
+func TestCoprimesInRange(t *testing.T) {
+	assert.Equal(t, []int{3, 7}, mathx.CoprimesInRange(10, 2, 7))
+	assert.Equal(t, []int{7, 9, 11, 13, 17, 19}, mathx.CoprimesInRange(10, 5, 20))
+}
+
+func TestMinorCoprimes(t *testing.T) {
+	assert.Equal(t, []int{1, 5}, mathx.MinorCoprimes(6))
+	assert.Equal(t, []int{1, 3, 7, 9}, mathx.MinorCoprimes(10))
+}
+
 func TestNextPrime(t *testing.T) {
 	assert.Equal(t, 2, mathx.NextPrime(0))
 	assert.Equal(t, 2, mathx.NextPrime(1))