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Minimum_Height_Trees.java
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Minimum_Height_Trees.java
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class Solution {
public List<Integer> findMinHeightTrees(int n, int[][] edges) {
if (n == 1) {
return Collections.singletonList(0);
}
List<Set<Integer>> graph = new ArrayList<>();
for (int i = 0; i < n; i++) {
graph.add(new HashSet<>());
}
for (int[] edge : edges) {
int u = edge[0];
int v = edge[1];
graph.get(u).add(v);
graph.get(v).add(u);
}
List<Integer> leaves = new ArrayList<>();
for (int i = 0; i < n; i++) {
if (graph.get(i).size() == 1) {
leaves.add(i);
}
}
while (n > 2) {
n -= leaves.size();
List<Integer> newLeaves = new ArrayList<>();
for (int leaf : leaves) {
int neighbor = graph.get(leaf).iterator().next();
graph.get(neighbor).remove(leaf);
if (graph.get(neighbor).size() == 1) {
newLeaves.add(neighbor);
}
}
leaves = newLeaves;
}
return leaves;
}
}