310. Minimum Height Trees, topological sorting, medium
explanation at gardner and tree
instead of whole array we just want the last level.
therefore erasing whole vector every time.
Code
```cpp
class Solution {
public:
vector findMinHeightTrees(int n, vector<vector>& edges) {
if (n == 1) return {0};
vector<vector> tree(n + 1);
vector indegree(n + 1, 0);
for (const auto& i: edges) {
int a = i[0], b = i[1];
tree[a].push_back(b);
tree[b].push_back(a);
indegree[a] ++;
indegree[b] ++;
}
queue qu;
for (int i = 0; i < indegree.size(); i++) {
if (indegree[i] == 1) {
qu.push(i);
}
}
vector topo;
while (!qu.empty()) {
int current_size = qu.size();
topo.clear();
for (int i = 0; i < current_size; i++) {
auto u = qu.front();
qu.pop();
topo.push_back(u);
for (const auto& v: tree[u]) {
if (--indegree[v] == 1) {
qu.push(v);
}
}
}
}
return topo;
}
};
```
</details>