题解 | #判断链表中是否有环#

/*
 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */

/**
 * 
 * @param head ListNode类 
 * @return bool布尔型
 */
function hasCycle( head ) {
    // write code here
    const circle = new Set()
    while(head){
        if(circle.has(head)){
            return true
        }
        circle.add(head)
        head = head.next
        
    }
    return false
}
module.exports = {
    hasCycle : hasCycle
};