What is the time complexity of LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List?

The Python solution on this page runs in O(n).

What is the space complexity of LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List?

The Python solution on this page uses O(n) auxiliary space.

MediumNo. 1171

Remove Zero Sum Consecutive Nodes from Linked List — LeetCode 1171 Python Solution

Pattern: Linked List
Topics: Hash Table, Linked List
Reading time: 4 min
Source: leetcode.com

The problem

Given the head of a linked list, we repeatedly delete consecutive sequences of nodes that sum to 0 until there are no such sequences. After doing so, return the head of the final linked list.

Example

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

Python solution

PythonSolution

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeZeroSumSublists(self, head: Optional[ListNode]) -> Optional[ListNode]:
        dummy = ListNode(next=head)
        last = {}
        s, cur = 0, dummy
        while cur:
            s += cur.val
            last[s] = cur
            cur = cur.next
        s, cur = 0, dummy
        while cur:
            s += cur.val
            cur.next = last[s].next
            cur = cur.next
        return dummy.next

Complexity

Time: O(n)
Space · auxiliary: O(n)

Pattern: Linked List

Rewire pointers in place, with a dummy head and a saved next to keep it safe. LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List is filed here because LeetCode tags it Linked List, which is the vocabulary this hub collects.

The linked list guide has the Python template for the pattern and the 75 LeetCode problems that use it.

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No.	Problem	Difficulty
0138	Copy List with Random Pointer	Medium
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0146	LRU Cache	Medium
0160	Intersection of Two Linked Lists	Easy
0355	Design Twitter	Medium

Frequently asked questions

How hard is LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List?: LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List is rated Medium on LeetCode.
What is the time complexity of LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List?: The Python solution on this page runs in O(n).
What is the space complexity of LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List cover?: LeetCode 1171. Remove Zero Sum Consecutive Nodes from Linked List is tagged Hash Table and Linked List on LeetCode.

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python

Please analyze this context and help me answer the question or solve the problem.

Transcript

"Okay, next one. Given a string, return the length of the longest substring that has no repeating characters. Walk me through your approach before you code it."

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

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Transcribing...

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python

Please analyze this context and help me answer the question or solve the problem.

Transcript

"Okay, next one. Given a string, return the length of the longest substring that has no repeating characters. Walk me through your approach before you code it."

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 TerraClear chat

Transcribing...

QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

90%Subscription

python

Please analyze this context and help me answer the question or solve the problem.

Transcript

"Okay, next one. Given a string, return the length of the longest substring that has no repeating characters. Walk me through your approach before you code it."

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 TerraClear chat

Transcribing...

Primary display

QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

The problem

Example

Python solution

Complexity

Pattern: Linked List

Related problems

Frequently asked questions

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Approach

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