Solutions and Summay for Linked List Naive and Easy Questions

1.Remove Linked List Elements

package linkedlist;
/*
 * Question: Remove all elements from a linked list of integers that have value val.
 */
public class RemoveLinkedListElements {

    /**
     * @param head a ListNode
     * @param val an integer
     * @return a ListNode
     */
    public static ListNode removeElements(ListNode head, int val) {
        // Write your code here
    	ListNode dummy = new ListNode(-1);
    	ListNode cur = dummy;
    	dummy.next = head;
    	while(cur.next != null){
    		if(cur.next.val == val){
    			cur.next = cur.next.next;
    		}
    		else{
    			cur = cur.next;
    		}
    	}
    	return dummy.next;
    }
}

2.Add Two Numbers

3.Delete Node in the Middle of Singly Linked List

4.Insertion Sort List

5.Merge Two Sorted Lists

6. Nth to Last Node in List

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @param n: An integer.
     * @return: Nth to last node of a singly linked list.
     */
    ListNode nthToLast(ListNode head, int n) {
        // write your code here
        ListNode dummy = new ListNode(0);
      dummy.next = head;
      ListNode walker = dummy;
      ListNode runner = dummy;
      while(runner.next != null && n>0){
          runner = runner.next;
          n--;
      }
      while(runner.next != null){
          runner = runner.next;
          walker = walker.next;
      }
      return walker.next;
  }
}

　　

7.Partition List

8.Remove Duplicates from Sorted List

9.Remove Nth Node From End of List

10.Reverse Linked List

11.Swap Nodes in Pairs