关于javascript:LeetCode-每日-2022-02-17

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虚构头节点 + 指针

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {*     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {const dummyHead = new ListNode(0, list1);
  let current = dummyHead;

  while(list1 !== null && list2 !== null) {if(list1.val < list2.val) {
      current.next = list1;
      list1 = list1.next;
    } else {
      current.next = list2;
      list2 = list2.next;
    }
    current = current.next;
  }

  current.next = list1 === null? list2 : list1;

  return dummyHead.next;
};

递归法

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {*     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {
    // 递归完结条件
    if(list1 === null) return list2;
    if(list2 === null) return list1;

    if(list1.val < list2.val) {list1.next = mergeTwoLists(list1.next, list2);
        return list1;
    } else {list2.next = mergeTwoLists(list1, list2.next);
        return list2;
    }
};

虚构头节点

/**
 * 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} val
 * @return {ListNode}
 */
var removeElements = function(head, val) {
  // 虚构头节点
  const dummyHead = new ListNode(0, head);
  let current = dummyHead;

  while(current && current.next) {
    // 只需找到要删除的节点的上一个节点
    if(current.next.val === val) current.next = current.next.next;
    else current = current.next;
  }

  return dummyHead.next;
};

虚构头节点 + 循环判断相等

/**
 * 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 deleteDuplicates = function(head) {if(!(head && head.next)) return head;

    const dummyHead = new ListNode(0, head);
    let current = dummyHead;

    while(current.next && current.next.next) {if(current.next.val === current.next.next.val) {
            const val = current.next.val;

            while(current.next && current.next.val === val) {current.next = current.next.next;}
        } else {current = current.next;}
    }

    return dummyHead.next;
};