Dado un árbol en forma de lista de adyacencia, tenemos que calcular la cantidad de Nodes en el subárbol de cada Node mientras calculamos la cantidad de Nodes en el subárbol de un Node en particular, ese Node también se agregará como un Node en el subárbol, por lo tanto, el número de Nodes en el subárbol de hojas es 1.
Ejemplos:
Input : Consider the Graph mentioned below:
Output : Nodes in subtree of 1 : 5 Nodes in subtree of 2 : 1 Nodes in subtree of 3 : 1 Nodes in subtree of 4 : 3 Nodes in subtree of 5 : 1 Input : Consider the Graph mentioned below:
Output : Nodes in subtree of 1 : 7 Nodes in subtree of 2 : 2 Nodes in subtree of 3 : 1 Nodes in subtree of 4 : 3 Nodes in subtree of 5 : 1 Nodes in subtree of 6 : 1 Nodes in subtree of 7 : 1
Explicación: Primero debemos calcular el recuento de valores [s]: el número de Nodes en el subárbol de Nodes s. Donde subárbol contiene el propio Node y todos los Nodes del subárbol de sus hijos. Por lo tanto, podemos calcular el número de Nodes de forma recursiva utilizando el concepto de DFS y DP, donde debemos procesar cada borde solo una vez y contar [] el valor de los niños utilizados para calcular el recuento [] de su padre expresando el concepto de DP (programación dinámica ).
Complejidad de tiempo: O(n) [en el procesamiento de todos los bordes (n-1)].
Algoritmo:
void numberOfNodes(int s, int e)
{
vector::iterator u;
cuenta1[s] = 1;
for (u = adj[s].begin(); u != adj[s].end(); u++)
{
// condición para omitir la ruta inversa
// ruta de los hijos a los padressi (*u == e)
continuar;
// llamada recursiva para DFSnumeroDeNodes(*u, s);
// actualiza el valor de cuenta[] del padre usando
// sus hijoscuenta1[s] += cuenta1[*u];
}}
Implementación:
C++
// CPP code to find number of nodes // in subtree of each node #include <bits/stdc++.h> using namespace std; const int N = 8; // variables used to store data globally int count1[N]; // adjacency list representation of tree vector<int> adj[N]; // function to calculate no. of nodes in a subtree void numberOfNodes(int s, int e) { vector<int>::iterator u; count1[s] = 1; for (u = adj[s].begin(); u != adj[s].end(); u++) { // condition to omit reverse path // path from children to parent if (*u == e) continue; // recursive call for DFS numberOfNodes(*u, s); // update count[] value of parent using // its children count1[s] += count1[*u]; } } // function to add edges in graph void addEdge(int a, int b) { adj[a].push_back(b); adj[b].push_back(a); } // function to print result void printNumberOfNodes() { for (int i = 1; i < N; i++) { cout << "\nNodes in subtree of " << i; cout << ": " << count1[i]; } } // driver function int main() { // insertion of nodes in graph addEdge(1, 2); addEdge(1, 4); addEdge(1, 5); addEdge(2, 6); addEdge(4, 3); addEdge(4, 7); // call to perform dfs calculation // making 1 as root of tree numberOfNodes(1, 0); // print result printNumberOfNodes(); return 0; }
Java
// A Java code to find number of nodes // in subtree of each node import java.util.ArrayList; public class NodesInSubtree { // variables used to store data globally static final int N = 8; static int count1[] = new int[N]; // adjacency list representation of tree static ArrayList<Integer> adj[] = new ArrayList[N]; // function to calculate no. of nodes in a subtree static void numberOfNodes(int s, int e) { count1[s] = 1; for(Integer u: adj[s]) { // condition to omit reverse path // path from children to parent if(u == e) continue; // recursive call for DFS numberOfNodes(u ,s); // update count[] value of parent using // its children count1[s] += count1[u]; } } // function to add edges in graph static void addEdge(int a, int b) { adj[a].add(b); adj[b].add(a); } // function to print result static void printNumberOfNodes() { for (int i = 1; i < N; i++) System.out.println("Node of a subtree of "+ i+ " : "+ count1[i]); } // Driver function public static void main(String[] args) { // Creating list for all nodes for(int i = 0; i < N; i++) adj[i] = new ArrayList<>(); // insertion of nodes in graph addEdge(1, 2); addEdge(1, 4); addEdge(1, 5); addEdge(2, 6); addEdge(4, 3); addEdge(4, 7); // call to perform dfs calculation // making 1 as root of tree numberOfNodes(1, 0); // print result printNumberOfNodes(); } } // This code is contributed by Sumit Ghosh
Python3
# Python3 code to find the number of # nodes in the subtree of each node N = 8 # variables used to store data globally count1 = [0] * (N) # Adjacency list representation of tree adj = [[] for i in range(N)] # Function to calculate no. of # nodes in subtree def numberOfNodes(s, e): count1[s] = 1 for u in adj[s]: # Condition to omit reverse path # path from children to parent if u == e: continue # recursive call for DFS numberOfNodes(u, s) # update count[] value of parent # using its children count1[s] += count1[u] # Function to add edges in graph def addEdge(a, b): adj[a].append(b) adj[b].append(a) # Function to print result def printNumberOfNodes(): for i in range(1, N): print("Nodes in subtree of", i, ":", count1[i]) # Driver Code if __name__ == "__main__": # insertion of nodes in graph addEdge(1, 2) addEdge(1, 4) addEdge(1, 5) addEdge(2, 6) addEdge(4, 3) addEdge(4, 7) # call to perform dfs calculation # making 1 as root of tree numberOfNodes(1, 0) # print result printNumberOfNodes() # This code is contributed by Rituraj Jain
C#
// C# code to find number of nodes // in subtree of each node using System; using System.Collections.Generic; class GFG { // variables used to store data globally static readonly int N = 8; static int []count1 = new int[N]; // adjacency list representation of tree static List<int> []adj = new List<int>[N]; // function to calculate no. of nodes in a subtree static void numberOfNodes(int s, int e) { count1[s] = 1; foreach(int u in adj[s]) { // condition to omit reverse path // path from children to parent if(u == e) continue; // recursive call for DFS numberOfNodes(u, s); // update count[] value of parent using // its children count1[s] += count1[u]; } } // function to add edges in graph static void addEdge(int a, int b) { adj[a].Add(b); adj[b].Add(a); } // function to print result static void printNumberOfNodes() { for (int i = 1; i < N; i++) Console.WriteLine("Node of a subtree of "+ i + " : "+ count1[i]); } // Driver Code public static void Main(String[] args) { // Creating list for all nodes for(int i = 0; i < N; i++) adj[i] = new List<int>(); // insertion of nodes in graph addEdge(1, 2); addEdge(1, 4); addEdge(1, 5); addEdge(2, 6); addEdge(4, 3); addEdge(4, 7); // call to perform dfs calculation // making 1 as root of tree numberOfNodes(1, 0); // print result printNumberOfNodes(); } } // This code is contributed by PrinciRaj1992
Javascript
<script> // A Javascript code to find number of nodes // in subtree of each node // variables used to store data globally let N = 8; let count1 = new Array(N); // adjacency list representation of tree let adj = new Array(N); // function to calculate no. of nodes in a subtree function numberOfNodes(s, e) { count1[s] = 1; for(let u = 0; u < adj[s].length; u++) { // condition to omit reverse path // path from children to parent if(adj[s][u] == e) continue; // recursive call for DFS numberOfNodes(adj[s][u] ,s); // update count[] value of parent using // its children count1[s] += count1[adj[s][u]]; } } // function to add edges in graph function addEdge(a, b) { adj[a].push(b); adj[b].push(a); } // function to print result function printNumberOfNodes() { for (let i = 1; i < N; i++) document.write("Node of a subtree of "+ i+ " : "+ count1[i] + "</br>"); } // Creating list for all nodes for(let i = 0; i < N; i++) adj[i] = []; // insertion of nodes in graph addEdge(1, 2); addEdge(1, 4); addEdge(1, 5); addEdge(2, 6); addEdge(4, 3); addEdge(4, 7); // call to perform dfs calculation // making 1 as root of tree numberOfNodes(1, 0); // print result printNumberOfNodes(); // This code is contributed by suresh07. </script>
Nodes in subtree of 1: 7 Nodes in subtree of 2: 2 Nodes in subtree of 3: 1 Nodes in subtree of 4: 3 Nodes in subtree of 5: 1 Nodes in subtree of 6: 1 Nodes in subtree of 7: 1
Ilustración de entrada y salida:
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