力扣刷题日记-234-回文链表

每天坚持刷题,刷爆leetcode需要多久????

• 给你一个单链表的头节点 head ，请你判断该链表是否为回文链表。如果是，返回 true ；否则，返回 false 。

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {boolean}
 */
var isPalindrome = function(head) {
    //反转链表
    const reverse = (head)=>{
        let p1 = head, p2 = null
        while(p1) {
            let tem = p1.next
            p1.next = p2
            p2 = p1
            p1 = tem
        }
        return p2
    }



    let f = head,s = head
    while(f != null && f.next != null) {
        f = f.next.next
        s = s.next
    }
    // 如果链表是奇数个,把中间的节点归到左边
    if(f != null) {
        s = s.next
    }
    s = reverse(s)
    f = head
    while(s != null) {
        if(f.val != s.val) return false
        f = f.next
        s = s.next
    }
    return true
};