rename directory

14_longest_collatz_sequence/main.go

@@ -0,0 +1,41 @@
+package main
+
+import "fmt"
+
+func main() {
+	num := 0
+	ml := 0
+	for i := 1000000; i > 1; i-- {
+		n := i
+		count := 1
+		for {
+			n = CollatzNext(n)
+			if n == 1 {
+				break
+			}
+			count++
+		}
+		if count > ml {
+			ml = count
+			num = i
+		}
+	}
+	fmt.Println("largest collatz is", num, "len:", ml)
+}
+
+func CollatzNext(n int) int {
+	if n == 1 {
+		return 1
+	} else if IsEven(n) {
+		return n / 2
+	} else {
+		return 3*n + 1
+	}
+}
+
+func IsEven(n int) bool {
+	if n > 1 && n%2 == 0 {
+		return true
+	}
+	return false
+}