✉️문제
https://leetcode.com/problems/reverse-linked-list/description/
Reverse Linked List - LeetCode
Can you solve this real interview question? Reverse Linked List - Given the head of a singly linked list, reverse the list, and return the reversed list. Example 1: [https://assets.leetcode.com/uploads/2021/02/19/rev1ex1.jpg] Input: head = [1,2,3,4,5] O
leetcode.com
🗝 문제풀이
public class ReverseLinkedList {
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; }
}
// 스택을 이용한 방법
public ListNode reverseList(ListNode head) {
if(head == null) return null;
ListNode root = head;
Stack<ListNode> stack = new Stack<>();
while(head != null) {
stack.push(head);
head = head.next;
}
ListNode res = stack.pop();
ListNode answer = res;
while(!stack.isEmpty()) {
ListNode tmp = stack.pop();
tmp.next = null;
res.next = tmp;
res = res.next;
}
return answer;
}
// 포인터를 이용한 방법
public ListNode reverseList2(ListNode head) {
ListNode prev = null;
ListNode current = head;
while(current != null) {
ListNode next = current.next;
current.next = prev;
prev = current;
current = next;
}
return prev;
}
}