1171. Remove Zero Sum Consecutive Nodes from Linked List

문제: https://leetcode.com/problems/remove-zero-sum-consecutive-nodes-from-linked-list/

Remove Zero Sum Consecutive Nodes from Linked List - LeetCode

 

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeZeroSumSublists(ListNode* head) {
        ListNode* node = head;
        
        ListNode* prev = new ListNode(-1001);
        ListNode* dummy = prev;
        prev->next = head;
        
        while(node){
            ListNode* curr = node;
            
            int s = 0;
            
            while(curr){
                s += curr->val;
                curr = curr->next;
                
                if(s == 0){
                    break;
                }
            }
            
            if(s == 0){
                prev->next = curr;
                node = prev->next;
            } else {
                prev = node;
                node = node->next;
            }
        }
        return dummy->next;
    }
};

Time complexity: O(N^2)

Space complexity: O(1)

 

 

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeZeroSumSublists(ListNode* head) {
        ListNode* dummy = new ListNode(0);
        
        dummy->next = head;
        
        unordered_map<int, ListNode*> pSums;
        
        ListNode* node = dummy;
        int pSum = 0;
        while(node){
            pSum += node->val;
            pSums[pSum] = node;
            
            node = node->next;
        }
        
        node = dummy;
        
        pSum = 0;
        while(node){
            pSum += node->val;
            node->next = pSums[pSum]->next;
            
            node = node->next;
        }
        
        return dummy->next;
    }
};

Time complexity: O(N)

Space complexity: O(N)