LeetCode 1171: Remove Zero Sum Consecutive Nodes from Linked List Solution
Master LeetCode problem 1171 (Remove Zero Sum Consecutive Nodes from Linked List), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
1171. Remove Zero Sum Consecutive Nodes from Linked List
Problem Explanation
Explanation
To solve this problem, we can use a hashmap to keep track of the running sum of the linked list nodes encountered so far. If we encounter the same running sum again, it means that the nodes between the two occurrences of the sum have a sum of 0. We can then remove those nodes from the linked list.
We iterate through the linked list, keeping track of the running sum and the node at which we first encountered that running sum. If we encounter the same running sum again, we remove all nodes between the two occurrences from the linked list.
We also need to handle the case where the running sum is 0 (i.e., the accumulated sum from the beginning of the list is 0). In this case, we remove all nodes up to the current node.
After processing the entire linked list, we return the head of the modified linked list.
Time complexity: O(n) where n is the number of nodes in the linked list. Space complexity: O(n) for the hashmap.
Solution Code
class Solution {
public ListNode removeZeroSumSublists(ListNode head) {
ListNode dummy = new ListNode(0);
dummy.next = head;
Map<Integer, ListNode> map = new HashMap<>();
int sum = 0;
for (ListNode curr = dummy; curr != null; curr = curr.next) {
sum += curr.val;
map.put(sum, curr);
}
sum = 0;
for (ListNode curr = dummy; curr != null; curr = curr.next) {
sum += curr.val;
curr.next = map.get(sum).next;
}
return dummy.next;
}
}Try It Yourself
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