Given a linked list, reverse it.

LinkedListReverse.java

//public class ListNode {
//	int val;
//	ListNode next;
//	ListNode(int x) { val = x; }
//}

public ListNode reverseList(ListNode head) {
    ListNode curr = head;
    ListNode prev = null, next = null;

    while(curr != null) {
        next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }

    return prev;
}