Linked List Cycle

Problem

• Return true if there is a cycle in the linked list. Otherwise, return false.

Approach

• 1. Keep looping the one node fast as twice as the other until they either run into eachother or exit the linked list

Reflections

I also did the hashmap version

func hasCycle(head *ListNode) bool {
    m := make(map[*ListNode]bool)

    node := head
    for node != nil {
        if m[node] {
            return true
        }
        m[node] = true
        node = node.Next
    }

    return false
}

Go Solution

func hasCycle(head *ListNode) bool {
    slow,fast := head,head
    for fast != nil && fast.Next != nil {
        slow = slow.Next
        fast = fast.Next.Next
        if slow == fast {
            return true
        }
    }

    return false
}