leetcode刷题日志01

question 2095

class Solution {
    public ListNode deleteMiddle(ListNode head) {
        int len=getLen(head);
        if(len==0) return null;
        float half=len/2.0f;
        if((len&1)==1){
            deleteNode(head,(int)Math.ceil(half));
            
        }else{
            deleteNode(head,(int)half);
        }
        return head;
        
    }
    public int getLen(ListNode head) {
        ListNode temp=head;
        int i=0;
        while(temp.next!=null){
            temp=temp.next;
            i++;
        }
        return i;
    }
    public void deleteNode(ListNode head,int n) {
        ListNode temp=head;
        int i=0;
        while(temp.next!=null){
            if(i==(n-1))break;
            temp=temp.next;
            i++;
        }
        temp.next=temp.next.next;
    }
}

question 143

class Solution {
    public void reorderList(ListNode head) {
        ListNode lastptr;
        ListNode nextptr;
        ListNode firstptr=head;
        ListNode targetptr=firstptr;

        if(!(head.next==null || head.next.next ==null)){
            lastptr=getLast(firstptr.next);
            while(targetptr.next!=null){
                nextptr=targetptr.next;
                targetptr.next=lastptr;
                lastptr.next=nextptr;
                targetptr=nextptr;
                lastptr=getLast(targetptr);
            }
            if(targetptr !=lastptr)
                targetptr.next=lastptr;
        }
    }
    public ListNode getLast(ListNode first) {
        ListNode last=first.next;
        ListNode temp=first;
        while(last !=null && last.next!=null){
            if (temp ==null)
                break;
            last=last.next;
            temp=temp.next;
        }
        temp.next=null;
        return last;
    }
}