题解 | #链表的中间结点#

/*
 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @return ListNode类
 */
function middleNode( head ) {
    if (head === null) return head;
    
    let fast = head;
    let slow = head;
    
    while (fast && fast.next) {
        fast = fast.next.next;
        slow = slow.next;
    }
    
    return slow;
}
module.exports = {
    middleNode : middleNode
};