Leetcode3
Leetcode3
- 203.移除链表元素
- 707.设计链表
- 206.反转链表
203.移除链表元素
Java
/** * Definition for singly-linked list. * 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; } * } */classSolution{publicListNoderemoveElements(ListNodehead,intval){ListNodenode0=newListNode(-1,head);ListNodecurrent=node0;while(current.next!=null){if(current.next.val==val){current.next=current.next.next;}else{current=current.next;}}returnnode0.next;}}用在链表中head前面添加一个节点node0
707.设计链表
classMyLinkedList{classLinkNode{intval;LinkNodenext;LinkNode(intval){this.val=val;}}intsize;LinkNodehead;publicMyLinkedList(){this.size=0;this.head=newLinkNode(0);}publicintget(intindex){LinkNodecurrent=head;for(inti=0;i<=index;i++){if(current.next==null){return-1;}current=current.next;}returncurrent.val;}publicvoidaddAtHead(intval){size++;LinkNodenode0=newLinkNode(val);node0.next=head.next;head.next=node0;}publicvoidaddAtTail(intval){LinkNodeendNode=newLinkNode(val);LinkNodecurrent=head;while(current.next!=null){current=current.next;}current.next=endNode;size++;}publicvoidaddAtIndex(intindex,intval){if(index<0||index>size){return;}LinkNodenode0=newLinkNode(val);LinkNodecurrent=head;for(inti=0;i<index;i++){current=current.next;}node0.next=current.next;current.next=node0;size++;}publicvoiddeleteAtIndex(intindex){if(index<0||index>=size){return;}LinkNodecurrent=head;for(inti=0;i<index;i++){current=current.next;}current.next=current.next.next;size--;}}/** * Your MyLinkedList object will be instantiated and called as such: * MyLinkedList obj = new MyLinkedList(); * int param_1 = obj.get(index); * obj.addAtHead(val); * obj.addAtTail(val); * obj.addAtIndex(index,val); * obj.deleteAtIndex(index); */206.反转链表
/** * Definition for singly-linked list. * 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; } * } */classSolution{publicListNodereverseList(ListNodehead){ListNodecurrent=head;ListNodepre=null;ListNodetemp0=null;while(current!=null){temp0=current.next;current.next=pre;pre=current;current=temp0;}returnpre;}}temp0 = current.next;
将下一个节提前保存，因为后面current.next指向了前面的节点。