亚信的实习的一到笔试题，交换链表的后半部分

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链表节点结构

package parameterValues;public class LNode {int value;LNode next;}

这是主程序

package parameterValues;import org.junit.Test;import sun.security.action.GetLongAction;public class LinkListParameter {/** * 交换链表后半部分的值，如果链表长度为偶数 * 则交换N/2个数 * 若链表长度为奇数 * 则交换(N+1)/2个数 */ public static void main(String[] args) {int a[] = {1,2,3,4,5,6};LNode head = initLNode(a);print(head);head = swapLinkList(head);print(head);}  private static LNode swapLinkList(LNode head) {int length = 0;LNode t = head;while( t != null){t = t.next;length++;}int mid = 0;if(length % 2 == 0){mid = length /2;}else{mid = (length+1)/2;}LNode newhead = new LNode();LNode nhead = newhead;newhead.value = head.value;newhead.next = head.next;System.out.println("mid ="+mid);int l=1;while(l<mid){LNode cur = new LNode();cur.value = getLNodeByIndex(head, l).value;cur.next = null;newhead.next = cur;newhead = cur;l++;}l = length-1;while(l>=mid && l<length){LNode cur = new LNode();cur.value = getLNodeByIndex(head,l).value;cur.next = null;newhead.next = cur;newhead = cur;l--;}print(nhead);return nhead;}private static LNode getLNodeByIndex(LNode head, int index) {LNode node = head;int x=0;while( x < index ){if(node.next == null ) return null;node = node.next;x++;}return node;}@Testpublic void getLNodeByIndexTest(){int a[] = {1,2,3,4,8,5,6,8,9};LNode head = initLNode(a);System.out.println(getLNodeByIndex(head, 7).value);}private static LNode initLNode(int[] a) { LNode list = new LNode(); LNode head; list.value = a[0]; list.next = null; head = list; for (int i = 1; i < a.length; i++) {LNode cur = new LNode();cur.value = a[i];list.next = cur;list = cur;} return head;}public static void print(LNode nd){ System.out.println("print out LNode list"); while(nd != null){ System.out.print(nd.value+" "); nd = nd.next; } System.out.println(); }}

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