Syncing Changes

go/prime-factors/prime.go

@@ -1,29 +1,49 @@
 package prime
 
-import (
-	"fmt"
-	"strconv"
-)
+import "fmt"
 
 const testVersion = 2
 
 var sieve []int64
+var iter int
 
 func Factors(num int64) []int64 {
-	var ret []int64
+	fmt.Println("Factors Called on ", num)
+	if num == 1 {
+		return []int64{}
+	}
 	for i := range sieve {
 		if sieve[i] == num {
+			// It's a prime already in the sieve
 			return []int64{num}
 		}
-	}
-	ret = []int64{}
-	for i := int64(2); i <= num; i++ {
-		fmt.Println("Testing " + strconv.Itoa(int(num)) + "%" + strconv.Itoa(int(i)) + " == " + strconv.Itoa(int(num%i)))
-		if num%i == 0 {
-			// It's a factor
-
-			ret = append(ret, i)
+		if num%sieve[i] == 0 {
+			div := (num / sieve[i])
+			return append([]int64{sieve[i]}, Factors(div)...)
 		}
 	}
-	return ret
+	// If we're here, we don't have the prime factors for this number
+	// Add 1 to the highest prime that we have and find the next prime
+	i := int64(2)
+	if len(sieve) > 0 {
+		i = sieve[len(sieve)-1]
+	}
+	fmt.Println("  Looking for a new prime starting at ", i)
+	for ; i <= num; i++ {
+		isPrime := true
+		for j := range sieve {
+			if i%sieve[j] == 0 {
+				isPrime = false
+			}
+			if !isPrime {
+				break
+			}
+		}
+		if isPrime {
+			sieve = append(sieve, i)
+			// New prime in the sieve, try again
+			return Factors(num)
+		}
+	}
+	return []int64{}
 }

go/prime-factors/primefactors_test.go

@@ -21,10 +21,10 @@ var tests = []struct {
 	{6, []int64{2, 3}},
 	{8, []int64{2, 2, 2}},
 	{9, []int64{3, 3}},
-	//	{27, []int64{3, 3, 3}},
-	//	{625, []int64{5, 5, 5, 5}},
-	//	{901255, []int64{5, 17, 23, 461}},
-	//	{93819012551, []int64{11, 9539, 894119}},
+	{27, []int64{3, 3, 3}},
+	{625, []int64{5, 5, 5, 5}},
+	{901255, []int64{5, 17, 23, 461}},
+	{93819012551, []int64{11, 9539, 894119}},
 }
 
 func TestPrimeFactors(t *testing.T) {
@@ -33,8 +33,12 @@ func TestPrimeFactors(t *testing.T) {
 	}
 	for _, test := range tests {
 		fmt.Print("Running Test: ")
-		fmt.Println(test)
+		fmt.Print(test)
+		fmt.Print(" :: ")
 		actual := Factors(test.input)
+		fmt.Print(actual)
+		fmt.Print("  Sieve: ")
+		fmt.Println(sieve)
 		if !reflect.DeepEqual(actual, test.expected) {
 			t.Errorf("prime.Factors(%d) = %v; expected %v",
 				test.input, actual, test.expected)