Jun 19, 2022 · Jun 14, 2022 · Jun 16, 2022
diff --git a/java/206. Reverse Linked List.java b/java/206. Reverse Linked List.java
 //Use three pointers and so you can change the next of the mid to the first one without losing the track of the original left.
 //Iterative version
 class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode p = null;
        ListNode q = null;
        ListNode r = head;
        while (r!=null) {
            p = q;
            q = r;
            r = r.next;
            q.next = p;
        }
        return q;
    }
 }

 //Recursive version
 class Solution {
    public ListNode reverseList(ListNode head) {
        return rev(head, null);
    }

    public ListNode rev(ListNode node, ListNode pre) {
        if (node == null)
            return pre;
        ListNode temp = node.next;
        node.next = pre;
        return rev(temp, node);
    }

 }
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,32 @@
		//Use three pointers and so you can change the next of the mid to the first one without losing the track of the original left.
		//Iterative version
		class Solution {
		public ListNode reverseList(ListNode head) {
		ListNode p = null;
		ListNode q = null;
		ListNode r = head;
		while (r!=null) {
		p = q;
		q = r;
		r = r.next;
		q.next = p;
		}
		return q;
		}
		}

		//Recursive version
		class Solution {
		public ListNode reverseList(ListNode head) {
		return rev(head, null);
		}

		public ListNode rev(ListNode node, ListNode pre) {
		if (node == null)
		return pre;
		ListNode temp = node.next;
		node.next = pre;
		return rev(temp, node);
		}

		}