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ReversedLinkedListII.java
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ReversedLinkedListII.java
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/**
* 92. Reversed LinkedList II
* 链表翻转
* @author LBW
*/
public class ReversedLinkedListII {
public ListNode reverseBetween(ListNode head, int left, int right) {
// 使用虚拟头节点避免分类讨论
ListNode dummy = new ListNode(-1);
dummy.next = head;
// 找到 left 前的节点和 right 后的节点
ListNode leftNode = dummy;
for (int i = 0; i < left - 1; i++) {
leftNode = leftNode.next;
}
ListNode cur = leftNode;
for (int i = 0; i < right - left + 1; i++) {
cur = cur.next;
}
// 切断,进行翻转
ListNode rightNode = cur.next;
cur.next = null;
ListNode reverseHead = reverse(leftNode.next);
// 连接
leftNode.next.next = rightNode;
leftNode.next = reverseHead;
return dummy.next;
}
private ListNode reverse(ListNode head) {
ListNode pre = null, cur = head, next = head.next;
while (cur != null) {
next = cur.next;
cur.next = pre;
pre = cur;
cur = next;
}
return pre;
}
}