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CenterOfTree.java
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CenterOfTree.java
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import java.util.ArrayList;
import java.util.List;
public class CenterOfTree {
public static List<Integer> seekCenterOfTree (List<Integer> graph[]) {
List<Integer> leaves = new ArrayList<>();
int degree[] = new int[graph.length];
int processedLeavesCnt = 0;
for (int i = 0; i < graph.length; i++) {
degree[i] = graph[i].size();
if (degree[i] == 1) {
leaves.add(i);
degree[i] = 0;
}
}
processedLeavesCnt = leaves.size();
while (processedLeavesCnt < graph.length) {
List<Integer> newLeaves = new ArrayList<>();
for (int node : leaves) {
for (int to : graph[node]) {
degree[to]--;
if (degree[to] == 1) {
newLeaves.add(to);
degree[to] = 0;
}
}
}
processedLeavesCnt += newLeaves.size();
leaves = newLeaves;
}
return leaves;
}
public static void addEdge(int a, int b, List<Integer> graph[]) {
graph[a].add(b);
graph[b].add(a);
}
/*
Sample Graph
0 - 6
|
1 - 2 - 3 - 5
|
4
Center of Tree is 2
*/
public static void main(String[] args) {
List<Integer> graph[] = new ArrayList[7];
for (int i = 0; i < graph.length; i++) {
graph[i] = new ArrayList<>();
}
addEdge(0, 2, graph);
addEdge(0, 6, graph);
addEdge(1, 2, graph);
addEdge(2, 3, graph);
addEdge(2, 4, graph);
addEdge(3, 5, graph);
List<Integer> result = seekCenterOfTree(graph);
for (int center : result)
// Output will be 2
System.out.print(center + " ");
}
}