Question

817. Linked List Components

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Description

You are given the head of a linked list containing unique integer values and an integer array nums that is a subset of the linked list values.

Return _the number of connected components in _nums_ where two values are connected if they appear consecutively in the linked list_.

 

Example 1:

Input: head = [0,1,2,3], nums = [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], nums = [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.

 

Constraints:

• The number of nodes in the linked list is n.
• 1 <= n <= 104
• 0 <= Node.val < n
• All the values Node.val are unique.
• 1 <= nums.length <= n
• 0 <= nums[i] < n
• All the values of nums are unique.

Solutions

Solution 1

# Definition for singly-linked list.
# class ListNode:
#   def __init__(self, val=0, next=None):
#     self.val = val
#     self.next = next
class Solution:
  def numComponents(self, head: Optional[ListNode], nums: List[int]) -> int:
    ans = 0
    s = set(nums)
    while head:
      while head and head.val not in s:
        head = head.next
      ans += head is not None
      while head and head.val in s:
        head = head.next
    return ans

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *   int val;
 *   ListNode next;
 *   ListNode() {}
 *   ListNode(int val) { this.val = val; }
 *   ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
  public int numComponents(ListNode head, int[] nums) {
    int ans = 0;
    Set<Integer> s = new HashSet<>();
    for (int v : nums) {
      s.add(v);
    }
    while (head != null) {
      while (head != null && !s.contains(head.val)) {
        head = head.next;
      }
      ans += head != null ? 1 : 0;
      while (head != null && s.contains(head.val)) {
        head = head.next;
      }
    }
    return ans;
  }
}

/**
 * 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:
  int numComponents(ListNode* head, vector<int>& nums) {
    unordered_set<int> s(nums.begin(), nums.end());
    int ans = 0;
    while (head) {
      while (head && !s.count(head->val)) head = head->next;
      ans += head != nullptr;
      while (head && s.count(head->val)) head = head->next;
    }
    return ans;
  }
};

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *   Val int
 *   Next *ListNode
 * }
 */
func numComponents(head *ListNode, nums []int) int {
  s := map[int]bool{}
  for _, v := range nums {
    s[v] = true
  }
  ans := 0
  for head != nil {
    for head != nil && !s[head.Val] {
      head = head.Next
    }
    if head != nil {
      ans++
    }
    for head != nil && s[head.Val] {
      head = head.Next
    }
  }
  return ans
}

/**
 * Definition for singly-linked list.
 * class ListNode {
 *   val: number
 *   next: ListNode | null
 *   constructor(val?: number, next?: ListNode | null) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 *   }
 * }
 */

function numComponents(head: ListNode | null, nums: number[]): number {
  const set = new Set<number>(nums);
  let res = 0;
  let cur = head;
  let inSet = false;
  while (cur != null) {
    if (set.has(cur.val)) {
      if (!inSet) {
        inSet = true;
        res++;
      }
    } else {
      inSet = false;
    }
    cur = cur.next;
  }
  return res;
}

// Definition for singly-linked list.
// #[derive(PartialEq, Eq, Clone, Debug)]
// pub struct ListNode {
//   pub val: i32,
//   pub next: Option<Box<ListNode>>
// }
//
// impl ListNode {
//   #[inline]
//   fn new(val: i32) -> Self {
//   ListNode {
//     next: None,
//     val
//   }
//   }
// }
use std::collections::HashSet;
impl Solution {
  pub fn num_components(head: Option<Box<ListNode>>, nums: Vec<i32>) -> i32 {
    let set = nums.into_iter().collect::<HashSet<i32>>();
    let mut res = 0;
    let mut in_set = false;
    let mut cur = &head;
    while let Some(node) = cur {
      if set.contains(&node.val) {
        if !in_set {
          in_set = true;
          res += 1;
        }
      } else {
        in_set = false;
      }
      cur = &node.next;
    }
    res
  }
}

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *   this.val = (val===undefined ? 0 : val)
 *   this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number[]} nums
 * @return {number}
 */
var numComponents = function (head, nums) {
  const s = new Set(nums);
  let ans = 0;
  while (head) {
    while (head && !s.has(head.val)) {
      head = head.next;
    }
    ans += head != null;
    while (head && s.has(head.val)) {
      head = head.next;
    }
  }
  return ans;
};