两两交换链表中的节点

题目链接：24
讲解链接：代码讲解

/**
 * 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 {ListNode}
 */
var swapPairs = function(head) {
    const dummyHead = new ListNode(0, head);
    // dummyHead.next = head;
    let temp = dummyHead;
    while (temp.next !== null && temp.next.next !== null) {
        const node1 = temp.next;
        const node2 = temp.next.next;
        temp.next = node2;
        node1.next = node2.next;
        node2.next = node1;
        temp = node1;
    }
    return dummyHead.next;
};

删除链表中倒数第N个节点

题目链接：19
讲解链接：代码讲解

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
    let dHead = new ListNode(0, head);
    let [slow,fast] = [dHead, dHead];
    let i = 0;
    while (i < n + 1) {
        fast = fast.next;
        i++;
    };
    while (fast !== null) {
        slow = slow.next;
        fast = fast.next;
    };
    slow.next = slow.next.next;
    return dHead.next;

};

链表相交

题目链接：链表相交
讲解链接：代码讲解

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} headA
 * @param {ListNode} headB
 * @return {ListNode}
 */
var getIntersectionNode = function(headA, headB) {
    let lenA = lenB = 0;
    let [curA, curB] = [headA, headB]
    while(headA) {
        lenA++;
        headA = headA.next;
    }
    // console.log("lenA:"+lenA);
    while(headB) {
        lenB++;
        headB = headB.next;
    }
    // console.log("lenB:"+lenB);
   if(lenA < lenB) {       // 让curA为最长链表的头，lenA为其长度
    
        // 交换变量注意加 “分号” ，两个数组交换变量在同一个作用域下时
        // 如果不加分号，下面两条代码等同于一条代码: [curA, curB] = [lenB, lenA]
        
        [curA, curB] = [curB, curA];
        [lenA, lenB] = [lenB, lenA];
    }
    let i = lenA - lenB;   // 求长度差
    while(i-- > 0) {       // 让curA和curB在同一起点上（末尾位置对齐）
        curA = curA.next;
    }
    while(curA && curA !== curB) {  // 遍历curA 和 curB，遇到相同则直接返回
        curA = curA.next;
        curB = curB.next;
    }
    return curA;
    
};

环形链表

题目链接：142
讲解链接：代码讲解

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var detectCycle = function(head) {
    if(!head || !head.next) return null;
    let slow =head.next, fast = head.next.next;
    while(fast && fast.next && fast!== slow) {
        slow = slow.next;
        fast = fast.next.next; 
    }
    if(!fast || !fast.next ) return null;
    //以上代码判断存不存在环，下面寻找环的入口节点
    //此时fast = slow，两个指针都在相遇节点
    slow = head;
    while (fast !== slow) {
        slow = slow.next;
        fast = fast.next;
    }
    return slow;
    
};

心得体会

坚持就是胜利！耶！每一天都元气满满！