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package class09;
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public class Code03_SmallerEqualBigger {
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public static class Node {
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public int value;
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public Node next;
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public Node(int data) {
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this.value = data;
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}
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}
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public static Node listPartition1(Node head, int pivot) {
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if (head == null) {
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return head;
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}
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Node cur = head;
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int i = 0;
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while (cur != null) {
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i++;
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cur = cur.next;
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}
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Node[] nodeArr = new Node[i];
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i = 0;
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cur = head;
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for (i = 0; i != nodeArr.length; i++) {
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nodeArr[i] = cur;
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cur = cur.next;
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}
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arrPartition(nodeArr, pivot);
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for (i = 1; i != nodeArr.length; i++) {
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nodeArr[i - 1].next = nodeArr[i];
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}
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nodeArr[i - 1].next = null;
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return nodeArr[0];
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}
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public static void arrPartition(Node[] nodeArr, int pivot) {
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int small = -1;
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int big = nodeArr.length;
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int index = 0;
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while (index != big) {
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if (nodeArr[index].value < pivot) {
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swap(nodeArr, ++small, index++);
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} else if (nodeArr[index].value == pivot) {
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index++;
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} else {
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swap(nodeArr, --big, index);
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}
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}
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}
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public static void swap(Node[] nodeArr, int a, int b) {
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Node tmp = nodeArr[a];
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nodeArr[a] = nodeArr[b];
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nodeArr[b] = tmp;
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}
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public static Node listPartition2(Node head, int pivot) {
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Node sH = null; // small head
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Node sT = null; // small tail
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Node eH = null; // equal head
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Node eT = null; // equal tail
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Node mH = null; // big head
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Node mT = null; // big tail
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Node next = null; // save next node
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// every node distributed to three lists
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while (head != null) {
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next = head.next;
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head.next = null;
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if (head.value < pivot) {
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if (sH == null) {
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sH = head;
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sT = head;
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} else {
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sT.next = head;
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sT = head;
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}
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} else if (head.value == pivot) {
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if (eH == null) {
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eH = head;
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eT = head;
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} else {
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eT.next = head;
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eT = head;
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}
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} else {
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if (mH == null) {
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mH = head;
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mT = head;
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} else {
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mT.next = head;
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mT = head;
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}
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}
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head = next;
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}
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// 小于区域的尾巴，连等于区域的头，等于区域的尾巴连大于区域的头
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if (sT != null) { // 如果有小于区域
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sT.next = eH;
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eT = eT == null ? sT : eT; // 下一步，谁去连大于区域的头，谁就变成eT
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}
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// 下一步，一定是需要用eT 去接 大于区域的头
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// 有等于区域，eT -> 等于区域的尾结点
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// 无等于区域，eT -> 小于区域的尾结点
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// eT 尽量不为空的尾巴节点
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if (eT != null) { // 如果小于区域和等于区域，不是都没有
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eT.next = mH;
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}
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return sH != null ? sH : (eH != null ? eH : mH);
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}
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public static void printLinkedList(Node node) {
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System.out.print("Linked List: ");
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while (node != null) {
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System.out.print(node.value + " ");
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node = node.next;
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}
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System.out.println();
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}
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public static void main(String[] args) {
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Node head1 = new Node(7);
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head1.next = new Node(9);
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head1.next.next = new Node(1);
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head1.next.next.next = new Node(8);
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head1.next.next.next.next = new Node(5);
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head1.next.next.next.next.next = new Node(2);
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head1.next.next.next.next.next.next = new Node(5);
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printLinkedList(head1);
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// head1 = listPartition1(head1, 4);
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head1 = listPartition2(head1, 5);
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printLinkedList(head1);
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}
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}
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