Some useful methods about into list.

/**
* Method 1: Delete the input element x
* And meanwhile keep the length of array after deleted n
* @ Param a Array
* @ Param n the length of array after deleted.
* @ Param x the element that need to be deleted.

*/

static void delete(int[] a, int n, int x) {// preconditions: [0] <= ... <= a[n-1], and n <= a.length;// postconditions: a[0] <= ... <= a[n-2], and x is deleted;int i = 0; // find the first index i for which a[i] > x:while (i < n && a[i] <= x) {++i;}// shift {a[i],...,a[n-1]} into {a[i-1],...,a[n-2]}:if (i < n - 1) {System.arraycopy(a, i, a, i - 1, n - i);}a[n - 1] = 0;}

/**
* Gets the number of nodes in the specified list;
* Fox example, if list is {33,55, 77,99}, the size (list) will be return 4;
*
* @ Param list
* @ Return
*/

static int size(Node list) {int size = 0;while (list != null) {++ size;list = list.next;}return size;}

/**
* Gets the sum of nodes in the specified list;
* Fox example, if list is {254, 55,}, the size (list) will be return;
* @ Param list
* @ Return
*/

static int sum(Node list){int sum = 0;while(list != null){sum += list.data;list = list.next;}return sum;}

/**
// Precondition: the specified list has at least two nodes;
// Postcondition: The last node in the list has been deleted;
For example, if list is {22, 44, 66, 88}, then removelast (list) will change it to {22, 44,66 }.
* @ Param list
*/

void removeLast(Node list){if(list == null || list.next == null){//throw new IllegalStatException();}//{33,55,77,99} while(list.next.next != null) {list = list.next;}list.next = null;} 

/**
*
* @ Param list
* @ Return
*/

static Node copy(Node list){if(list == null){return null;}Node clone = new Node(list.data);for (Node p = list, q = clone; p != null; p = p.next, q = q.next){q.next = p.next;}return clone;}

/**
* Get a new list that contains copies of the P-Q nodes of the specified list,
* Starting with node number P (starting with 0 ).
* For example, if listis {22, 33, 44, 55, 66, 77, 88, 99}, then sublist (list, 2, 7) will
* Return the new list {44, 55, 66, 77, 88}. Note that the two lists must be completely independent of each other.
* Changing one list shocould have no effect upon the other.
* @ Param list
* @ Param m
* @ Param n
* @ Return
*/

Node sublist(Node list, int m, int n) {if (m < 0 || n < m) {throw new IllegalArgumentException();} else if (n == m) {return null;}//55,22,11,33for (int i = 0; i < m; i++) {list = list.next;}Node clone = new Node(list.data);Node p = list, q = clone;for (int i = m + 1; i < n; i++) {if (p.next == null) {throw new IllegalArgumentException();}q.next = new Node(p.next.data);p = p.next;q = q.next;}return clone;}