Sum of dependencies in a graph


08 Jul, 2022

Given a directed and connected graph with n nodes. If there is an edge from u to v then u depends on v. Our task was to find out the sum of dependencies for every node. 
Example: 
For the graph in diagram, 
A depends on C and D i.e. 2 
B depends on C i.e. 1 
D depends on C i.e. 1 
And C depends on none. 
Hence answer -> 0 + 1 + 1 + 2 = 4
Asked in : Flipkart Interview
Idea is to check adjacency list and find how many edges are there from each vertex and return the total number of edges. 
Implementation:
C++
Java
Python3
C#
 

 
 










// C++ program to find the sum of dependencies
#include <bits/stdc++.h>
using namespace std;
 
// To add an edge
void addEdge(vector <int> adj[], int u,int v)
{
    adj[u].push_back(v);
}
 
// find the sum of all dependencies
int findSum(vector<int> adj[], int V)
{
    int sum = 0;
 
    // just find the size at each vector's index
    for (int u = 0; u < V; u++)
        sum += adj[u].size();
 
    return sum;
}
 
// Driver code
int main()
{
    int V = 4;
    vector<int >adj[V];
    addEdge(adj, 0, 2);
    addEdge(adj, 0, 3);
    addEdge(adj, 1, 3);
    addEdge(adj, 2, 3);
 
    cout << "Sum of dependencies is "
         << findSum(adj, V);
    return 0;
}






 

 
 










// Java program to find the sum of dependencies
 
import java.util.Vector;
 
class Test
{
    // To add an edge
    static void addEdge(Vector <Integer> adj[], int u,int v)
    {
        adj[u].addElement((v));
    }
     
    // find the sum of all dependencies
    static int findSum(Vector<Integer> adj[], int V)
    {
        int sum = 0;
      
        // just find the size at each vector's index
        for (int u = 0; u < V; u++)
            sum += adj[u].size();
      
        return sum;
    }
     
    // Driver method
    public static void main(String[] args) 
    {
        int V = 4;
          @SuppressWarnings("unchecked")
        Vector<Integer> adj[] = new Vector[V];
         
        for (int i = 0; i < adj.length; i++) {
            adj[i] = new Vector<>();
        }
         
        addEdge(adj, 0, 2);
        addEdge(adj, 0, 3);
        addEdge(adj, 1, 3);
        addEdge(adj, 2, 3);
      
        System.out.println("Sum of dependencies is " +
                            findSum(adj, V));
    }
}
// This code is contributed by Gaurav Miglani






 

 
 










# Python3 program to find the sum 
# of dependencies
 
# To add an edge
def addEdge(adj, u, v):
 
    adj[u].append(v)
 
# Find the sum of all dependencies
def findSum(adj, V):
     
    sum = 0
     
    # Just find the size at each 
    # vector's index
    for u in range(V):
        sum += len(adj[u])
         
    return sum
 
# Driver code
if __name__=='__main__':
 
    V = 4
    adj = [[] for i in range(V)]
     
    addEdge(adj, 0, 2)
    addEdge(adj, 0, 3)
    addEdge(adj, 1, 3)
    addEdge(adj, 2, 3)
     
    print("Sum of dependencies is",
          findSum(adj, V))
     
# This code is contributed by rutvik_56






 

 
 










// C# program to find the sum of dependencies
using System;
using System.Collections;
 
class GFG{
     
// To add an edge
static void addEdge(ArrayList []adj, int u,
                                     int v)
{
    adj[u].Add(v);
}
 
// Find the sum of all dependencies
static int findSum(ArrayList []adj, int V)
{
    int sum = 0;
     
    // Just find the size at each 
    // vector's index
    for(int u = 0; u < V; u++)
        sum += adj[u].Count;
  
    return sum;
}
 
// Driver code
public static void Main(string[] args) 
{
    int V = 4;
       
    ArrayList []adj = new ArrayList[V];
     
    for(int i = 0; i < V; i++)
    {
        adj[i] = new ArrayList();
    }
     
    addEdge(adj, 0, 2);
    addEdge(adj, 0, 3);
    addEdge(adj, 1, 3);
    addEdge(adj, 2, 3);
  
    Console.Write("Sum of dependencies is " +
                  findSum(adj, V));
}
}
 
// This code is contributed by pratham76






Sum of dependencies is 4
Time complexity: O(V) where V is number of vertices in graph.
This article is contributed by Sahil Chhabra (akku). If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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