forked from shuboc/LeetCode-2
-
Notifications
You must be signed in to change notification settings - Fork 0
/
graph-valid-tree.cpp
45 lines (42 loc) · 1.19 KB
/
graph-valid-tree.cpp
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
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
// Time: O(|V| + |E|)
// Space: O(|V|)
class Solution {
public:
struct node {
int parent;
vector<int>neighbors;
};
bool validTree(int n, vector<pair<int, int>>& edges) {
if (edges.size() != n - 1) {
return false;
}
unordered_map<int, node> nodes;
for (const auto& edge : edges) {
nodes[edge.first].neighbors.emplace_back(edge.second);
nodes[edge.second].neighbors.emplace_back(edge.first);
}
for (int i = 0; i < n; ++i) {
nodes[i].parent = -1;
}
unordered_set<int> visited;
queue<int> q;
q.emplace(0);
while (!q.empty()) {
int i = q.front();
q.pop();
visited.insert(i);
for (const auto& n : nodes[i].neighbors) {
if (n != nodes[i].parent) {
if (visited.find(n) != visited.end()) {
return false;
} else {
visited.insert(n);
nodes[n].parent = i;
q.emplace(n);
}
}
}
}
return true;
}
};