1171. Remove Zero Sum Consecutive Nodes from Linked List

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.  You may return any such answer.

 

(Note that in the examples below, all sequences are serializations of ListNode objects.)

Example 1:

Input: head = [1,2,-3,3,1]
Output: [3,1]
Note: The answer [1,2,1] would also be accepted.

Example 2:

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

Example 3:

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

 

Constraints:

  • The given linked list will contain between 1 and 1000 nodes.
  • Each node in the linked list has -1000 <= node.val <= 1000.

Rust Solution

struct Solution;
use rustgym_util::*;

use std::collections::HashMap;

impl Solution {
    fn remove_zero_sum_sublists(mut head: ListLink) -> ListLink {
        let mut stack: Vec<i32> = vec![];
        let mut hm: HashMap<i32, usize> = HashMap::new();
        let mut sum = 0;
        hm.insert(0, 0);
        while let Some(node) = head {
            let val = node.val;
            head = node.next;
            if val == 0 {
                continue;
            }
            sum += val;
            if let Some(&size) = hm.get(&sum) {
                sum -= val;
                while stack.len() > size {
                    let top = stack.pop().unwrap();
                    hm.remove(&sum);
                    sum -= top;
                }
            } else {
                stack.push(val);
                hm.insert(sum, stack.len());
            }
        }
        let mut prev = None;
        while let Some(top) = stack.pop() {
            prev = ListLink::link(top, prev);
        }
        prev
    }
}

#[test]
fn test() {
    let head = list!(1, 2, -3, 3, 1);
    let res = list!(3, 1);
    assert_eq!(Solution::remove_zero_sum_sublists(head), res);
    let head = list!(1, 2, 3, -3, 4);
    let res = list!(1, 2, 4);
    assert_eq!(Solution::remove_zero_sum_sublists(head), res);
    let head = list!(1, 2, 3, -3, -2);
    let res = list!(1);
    assert_eq!(Solution::remove_zero_sum_sublists(head), res);
}

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