817. Linked List Components

We are given head, the head node of a linked list containing unique integer values.

We are also given the list G, a subset of the values in the linked list.

Return the number of connected components in G, where two values are connected if they appear consecutively in the linked list.

Example 1:

Input: 
head: 0->1->2->3
G = [0, 1, 3]
Output: 2
Explanation: 
0 and 1 are connected, so [0, 1] and [3] are the two connected components.

Example 2:

Input: 
head: 0->1->2->3->4
G = [0, 3, 1, 4]
Output: 2
Explanation: 
0 and 1 are connected, 3 and 4 are connected, so [0, 1] and [3, 4] are the two connected components.

Note:

  • If N is the length of the linked list given by head, 1 <= N <= 10000.
  • The value of each node in the linked list will be in the range [0, N - 1].
  • 1 <= G.length <= 10000.
  • G is a subset of all values in the linked list.

Rust Solution

struct Solution;
use rustgym_util::*;
use std::collections::HashSet;
use std::iter::FromIterator;

impl Solution {
    fn num_components(head: ListLink, g: Vec<i32>) -> i32 {
        let mut p = head;
        let hs: HashSet<i32> = HashSet::from_iter(g);
        let mut open = false;
        let mut res = 0;
        while let Some(node) = p {
            if hs.contains(&node.val) {
                if !open {
                    open = true;
                }
            } else {
                if open {
                    open = false;
                    res += 1;
                }
            }
            p = node.next;
        }
        if open {
            res += 1;
        }
        res
    }
}

#[test]
fn test() {
    let head = list!(0, 1, 2, 3);
    let g = vec![0, 1, 3];
    let res = 2;
    assert_eq!(Solution::num_components(head, g), res);
    let head = list!(0, 1, 2, 3, 4);
    let g = vec![0, 3, 1, 4];
    let res = 2;
    assert_eq!(Solution::num_components(head, g), res);
}

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