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Copy pathLinkedListMergeSort.java
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127 lines (104 loc) · 3.23 KB
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package com.crossoverjie.algorithm;
/**
* 链表排序, 建议使用归并排序
*
* @author 6563699600@qq.com
* @date 6/7/2018 11:42 PM
* @since 1.0
*/
public class LinkedListMergeSort {
final static class Node {
int e;
Node next;
public Node() {
}
public Node(int e, Node next) {
this.e = e;
this.next = next;
}
}
public Node mergeSort(Node first, int length) {
if (length == 1) {
return first;
} else {
Node middle = new Node();
Node tmp = first;
/**
* 后期会对这里进行优化，通过一次遍历算出长度和中间元素
*/
for (int i = 0; i < length; i++) {
if (i == length / 2) {
break;
}
middle = tmp;
tmp = tmp.next;
}
/**
* 这里是链表归并时要注意的细节
*/
Node right = middle.next;
middle.next = null;
Node leftStart = mergeSort(first, length / 2);
Node rightStart;
if (length % 2 == 0) {
rightStart = mergeSort(right, length / 2);
} else {
rightStart = mergeSort(right, length / 2 + 1);
}
return mergeList(leftStart, rightStart);
}
}
public Node mergeList(Node left, Node right) {
Node head = new Node();
Node result = head;
/**
* 思想就是两个链表同时遍历，将更的元素插入结果中，同时更更大的元素所属的链表的指针向下移动
*/
while (!(null == left && null == right)) {
Node tmp;
if (left == null) {
result.next = right;
break;
} else if (right == null) {
result.next = left;
break;
} else if (left.e >= right.e) {
tmp = left;
result.next = left;
result = tmp;
left = left.next;
} else {
tmp = right;
result.next = right;
result = tmp;
right = right.next;
}
}
return head.next;
}
public static void main(String[] args) {
Node head = new Node();
head.next = new Node(7,
new Node(2,
new Node(5,
new Node(4,
new Node(3,
new Node(6,
new Node(11, null)
)
)
)
)
)
);
int length = 0;
for (Node e = head.next; null != e; e = e.next) {
length++;
}
LinkedListMergeSort sort = new LinkedListMergeSort();
head.next = sort.mergeSort(head.next, length);
for (Node n = head.next; n != null; n = n.next) {
System.out.println(n.e);
}
}
}