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.

c++代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    int numComponents(ListNode* head, vector<int>& G) {
        int res=0;
        set<int> s;
        for(auto&g: G)
            s.insert(g);
        bool enter=false;
        //bool leave=false;
        while(head){
            if(s.find(head->val)!=s.end())
            {
                if(enter==false)
                {
                    enter=true;
                    res+=1;
                }
                
            }else
            {
                enter=false;
            }
            head=head->next;
        }
        return res;
    }
};

python代码

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def numComponents(self, head, G):
        """
        :type head: ListNode
        :type G: List[int]
        :rtype: int
        """
        cnt=0
        enter=False
        while head is not None:
            if head.val in G:
                if not enter:
                    enter=True
                    cnt+=1
            else:
                enter=False
            #print "head.val: {}, cnt: {}".format(head.val,cnt)
                
            head=head.next
            
        return cnt