[JS] Remove Duplicates from Sorted List II

🔒 문제 (LeetCode 82)

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

Constraints:

• The number of nodes in the list is in the range [0, 300].
• -100 <= Node.val <= 100
• The list is guaranteed to be sorted in ascending order.

 

🌊 입출력

Example 1:

Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]

Example 2:

Input: head = [1,1,1,2,3]
Output: [2,3]

 

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🔑 해결

🌌 알고리즘 - 투포인터

첫번째 노드가 중복되어 제거할 경우를 고려하여, dummy를 head 앞에 붙여 노드 제거를 수행한다. 

/**
 * 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) {
    const dummy = new ListNode();
    dummy.next = head;
    let node = dummy;
    
    while(node.next) {
        if(node.next.next && node.next.val === node.next.next.val) {
            let nextNode = node.next.next.next;
            while(nextNode && nextNode.val === node.next.val) {
                nextNode = nextNode.next;
            }
            node.next = nextNode;
        } else {
            node = node.next
        }
    }
    
    return dummy.next;
};