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Sum of dependencies in a graph
• Difficulty Level : Basic
• Last Updated : 02 Dec, 2020

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.

## C++

 `// C++ program to find the sum of dependencies``#include ``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

 `// Java program to find the sum of dependencies`` ` `import` `java.util.Vector;`` ` `class` `Test``{``    ``// To add an edge``    ``static` `void` `addEdge(Vector adj[], ``int` `u,``int` `v)``    ``{``        ``adj[u].addElement((v));``    ``}``     ` `    ``// find the sum of all dependencies``    ``static` `int` `findSum(Vector 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 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

 `# 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#

 `// 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`

Output:

`Sum of dependencies is 4`

Time complexity: O(V) where V is number of vertices in graph.

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