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SortList.java
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SortList.java
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package com.dbc;
public class SortList {
public class ListNode {
int val;
ListNode next;
ListNode() {
}
ListNode(int val) {
this.val = val;
}
ListNode(int val, ListNode next) {
this.val = val;
this.next = next;
}
}
private ListNode mergeSort(ListNode node, int length) {
if (length <= 1) return node;
ListNode remain = node;
for (int i = 1; i < length / 2; i++) remain = remain.next;
ListNode temp = remain.next;
remain.next = null;
ListNode leftNode = mergeSort(node, length / 2);
ListNode rightNode = mergeSort(temp, length - length / 2);
ListNode preHead = new ListNode();
ListNode res = preHead;
while (leftNode != null && rightNode != null) {
if (leftNode.val <= rightNode.val) {
preHead.next = leftNode;
leftNode = leftNode.next;
} else {
preHead.next = rightNode;
rightNode = rightNode.next;
}
preHead = preHead.next;
}
preHead.next = leftNode != null ? leftNode : rightNode;
return res.next;
}
public ListNode sortList(ListNode head) {
int length = 0;
ListNode temp = head;
while (temp != null) {
temp = temp.next;
length++;
}
return mergeSort(head, length);
}
}