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CountNumberOfNodesInSubtree.java
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CountNumberOfNodesInSubtree.java
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package Graph;
import java.lang.reflect.Array;
import java.util.*;
/**
* @author kalpak
*
*
*/
public class CountNumberOfNodesInSubtree {
public static List<List<Integer>> createGraph(int numNodes) {
List<List<Integer>> graphAdjList = new ArrayList<>();
for (int i = 0; i < numNodes; i++)
graphAdjList.add(new ArrayList<>());
return graphAdjList;
}
public static void addUndirectedEdge(List<List<Integer>> graph, int from, int to) {
graph.get(from).add(to);
graph.get(to).add(from);
}
public static void getNumberOfNodesInSubtree(List<List<Integer>> graph, int numNodes) {
int[] count = new int[numNodes];
boolean[] isVisited = new boolean[numNodes];
dfsCountNodesInSubtreeRecursive(graph, isVisited, count, 1);
System.out.println(Arrays.toString(count));
}
private static int dfsCountNodesInSubtreeRecursive(List<List<Integer>> graph, boolean[] isVisited, int[] count, int startNode) {
isVisited[startNode] = true;
int current_size = 1;
List<Integer> adjacencyList = graph.get(startNode);
for(int child : adjacencyList) {
if(!isVisited[child]) {
current_size += dfsCountNodesInSubtreeRecursive(graph, isVisited, count, child);
}
}
count[startNode] = current_size;
return current_size;
}
public static void main(String[] args) {
int numNodes = 8;
List<List<Integer>> graph = createGraph(numNodes);
addUndirectedEdge(graph, 0, 1);
addUndirectedEdge(graph, 1, 2);
addUndirectedEdge(graph, 2, 3);
addUndirectedEdge(graph, 2, 4);
addUndirectedEdge(graph, 3, 7);
addUndirectedEdge(graph, 4, 5);
addUndirectedEdge(graph, 4, 6);
getNumberOfNodesInSubtree(graph, numNodes);
}
}