Linked List Components Problem
Description
LeetCode Problem 817.
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:
1
2
3
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:
1
2
3
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 <= 10^4
- 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.
Sample C++ Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/**
* 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> map(nums.begin(),nums.end());
int ans = 0;
bool lastMatch = 0;
while (head){
if (map.find(head->val) == map.end()) {
lastMatch = 0;
} else {
if (!lastMatch) {
ans++;
lastMatch = 1;
}
}
head = head->next;
}
return ans;
}
};