解法一:常规解法,建图+DFS,时间复杂度O(n)+O(n),空间复杂度因为需要存储图,所以是O(n)
这种方法是通解,对于所有图都适用。
/**
* 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) {
unordered_set<int> f(G.begin(), G.end());
unordered_map<int, vector<int>> g;
//根据G中节点,从list中建立图g
int u = head->val;
while(head->next) {
head = head->next;
int v = head->val;
if(f.count(v) && f.count(u)) {
g[u].push_back(v);
g[v].push_back(u);
}
u = v;
}
//DFS
int ans = 0;
unordered_set<int> visited;
for(int u