[LeetCode] linked list

反转链表

递归

var reverseList = function(head) {
    if (!head.next || !head ) return head  // if console.log will get 1,2,3,4,5
    const prev = reverseList(head.next)
    head.next.next = head   // if console.log here will get 5,4,3,2,1
    head.next = null
    return prev
};

双指针

var reverseList = function(head) {
    let prev = null
    let curr = head
    while(curr) {
        let temp = curr.next
        curr.next = prev
        prev = curr
        curr = temp
    }
    return prev
};