初始:两个指针都指向dummy 第一个指针faster先走k步,然后两个指针一起走,直到faster指针==null,此时lower指针指向的就是倒数第k个结点。 特殊情况:
/*
public class ListNode {
int val;
ListNode next = null;
ListNode(int val) {
this.val = val;
}
}*/
public class ListKNode {
public ListNode FindKthToTail(ListNode head,int k) {
if(head == null || k<=0) {
return null;
}
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode faster = dummy, lower = dummy;
for(int i=0; i<k; i++) {
if(faster == null) {
return null;
} else {
faster = faster.next;
}
}
while(faster!=null) {
faster = faster.next;
lower = lower.next;
}
return (lower==dummy) ? null : lower;
}
}