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206-Reverse-Linked-List.js
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206-Reverse-Linked-List.js
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/**
* https://leetcode.com/problems/reverse-linked-list/
* Time O(N) | Space O(N)
* @param {ListNode} head
* @return {ListNode}
*/
var reverseList = function (head) {
const isBaseCase = !head?.next;
if (isBaseCase) return head;
return dfs(head); /* Time O(N) | Space O(N) */
}
const dfs = (curr) => {
const prev = reverseList(curr.next);/* Time O(N) | Space O(N) */
curr.next.next = curr;
curr.next = null;
return prev;
}
/**
* https://leetcode.com/problems/reverse-linked-list/
* Time O(N) | Space O(1)
* @param {ListNode} head
* @return {ListNode}
*/
var reverseList = function (head) {
let [ prev, curr, next ] = [ null, head, null ];
while (curr) {/* Time O(N) */
next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
return prev;
};