# Sum of degrees of all nodes of a undirected graph

Given an edge list of a graph we have to find the sum of degree of all nodes of a undirected graph.
Example Examples:

```Input : edge list : (1, 2), (2, 3), (1, 4), (2, 4)
Output : sum= 8

```

Brute force approach
We will add the degree of each node of the graph and print the sum.

## C++

 `// C++ implementation of above approach ` `#include ` `using` `namespace` `std; ` ` `  `// returns the sum of degree of all ` `// the nodes in a undirected graph ` `int` `count(``int` `edges[], ``int` `len, ``int` `n) ` `{ ` `    ``int` `degree[n + 1] = { 0 }; ` ` `  `    ``// compute the degree of each node ` `    ``for` `(``int` `i = 0; i < len; i++) { ` ` `  `        ``// increase the degree of the ` `        ``// nodes ` `        ``degree[edges[i]]++; ` `        ``degree[edges[i]]++; ` `    ``} ` ` `  `    ``// calculate the sum of degree ` `    ``int` `sum = 0; ` `    ``for` `(``int` `i = 1; i <= n; i++) ` `        ``sum += degree[i]; ` ` `  `    ``return` `sum; ` `} ` ` `  `// main function ` `int` `main() ` `{ ` `    ``// the edge list ` `    ``int` `edges[] = { { 1, 2 }, ` `                       ``{ 2, 3 }, ` `                       ``{ 1, 4 }, ` `                       ``{ 2, 4 } }; ` `    ``int` `len = ``sizeof``(edges) / (``sizeof``(``int``) * 2), n = 4; ` ` `  `    ``// display the result ` `    ``cout << ``"sum = "` `<< count(edges, len, n) << endl; ` `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `class` `GFG { ` ` `  `    ``// returns the sum of degree of all ` `    ``// the nodes in a undirected graph ` `    ``static` `int` `count(``int` `edges[][], ``int` `len, ``int` `n) ` `    ``{ ` `        ``int` `degree[] = ``new` `int``[n + ``1``]; ` ` `  `        ``// compute the degree of each node ` `        ``for` `(``int` `i = ``0``; i < len; i++) { ` ` `  `            ``// increase the degree of the ` `            ``// nodes ` `            ``degree[edges[i][``0``]]++; ` `            ``degree[edges[i][``1``]]++; ` `        ``} ` ` `  `        ``// calculate the sum of degree ` `        ``int` `sum = ``0``; ` `        ``for` `(``int` `i = ``1``; i <= n; i++) ` `            ``sum += degree[i]; ` ` `  `        ``return` `sum; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``// the edge list ` `        ``int` `edges[][] = { { ``1``, ``2` `}, ` `                          ``{ ``2``, ``3` `}, ` `                          ``{ ``1``, ``4` `}, ` `                          ``{ ``2``, ``4` `} }; ` `        ``int` `len = edges.length, n = ``4``; ` ` `  `        ``// display the result ` `        ``System.out.println(``"sum = "` `+ count(edges, len, n)); ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

## Python3

 `# Python 3 implementation of above approach ` ` `  `# returns the sum of degree of all ` `# the nodes in a undirected graph ` `def` `count(edges, len1, n): ` `    ``degree ``=` `[``0` `for` `i ``in` `range``(n ``+` `1``)] ` ` `  `    ``# compute the degree of each node ` `    ``for` `i ``in` `range``(len1): ` `        ``# increase the degree of the ` `        ``# nodes ` `        ``degree[edges[i][``0``]] ``+``=` `1` `        ``degree[edges[i][``1``]] ``+``=` `1` ` `  `    ``# calculate the sum of degree ` `    ``sum` `=` `0` `    ``for` `i ``in` `range``(``1``, n ``+` `1``, ``1``): ` `        ``sum` `+``=` `degree[i] ` ` `  `    ``return` `sum` ` `  `# main function ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``# the edge list ` `    ``edges ``=` `[[``1``, ``2``], [``2``, ``3``], [``1``, ``4``], [``2``, ``4``]] ` `    ``len1 ``=` `len``(edges) ` `    ``n ``=` `4` ` `  `    ``# display the result ` `    ``print``(``"sum ="``, count(edges, len1, n)) ` `     `  `# This code is contributed by ` `# Surendra_Gangwar `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// returns the sum of degree of all ` `    ``// the nodes in a undirected graph ` `    ``static` `int` `count(``int``[][] edges, ``int` `len, ``int` `n) ` `    ``{ ` `        ``int``[] degree = ``new` `int``[n + 1]; ` ` `  `        ``// compute the degree of each node ` `        ``for` `(``int` `i = 0; i < len; i++) { ` ` `  `            ``// increase the degree of the ` `            ``// nodes ` `            ``degree[edges[i]]++; ` `            ``degree[edges[i]]++; ` `        ``} ` ` `  `        ``// calculate the sum of degree ` `        ``int` `sum = 0; ` `        ``for` `(``int` `i = 1; i <= n; i++) ` `            ``sum += degree[i]; ` ` `  `        ``return` `sum; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``// the edge list ` `        ``int``[][] edges = ``new` `int``[][] { ``new` `int``[] { 1, 2 }, ` `                                      ``new` `int``[] { 2, 3 }, ` `                                      ``new` `int``[] { 1, 4 }, ` `                                      ``new` `int``[] { 2, 4 } }; ` `        ``int` `len = edges.Length, n = 4; ` ` `  `        ``// display the result ` `        ``Console.WriteLine(``"sum = "` `+ count(edges, len, n)); ` `    ``} ` `} ` ` `  `// This code has been contributed by Code_Mech. `

## PHP

 ` `

Output:

`sum = 8`

Efficient approach
If we get the number of the edges in a directed graph then we can find the sum of degree of the graph. Let us consider an graph with no edges. If we add a edge we are increasing the degree of two nodes of graph by 1, so after adding each edge the sum of degree of nodes increases by 2, hence the sum of degree is 2*e.

## C++

 `// C++ implementation of above approach ` `#include ` `using` `namespace` `std; ` ` `  `// returns the sum of degree of all ` `// the nodes in a undirected graph ` `int` `count(``int` `edges[], ``int` `len) ` `{ ` `    ``return` `2 * len; ` `} ` ` `  `// main function ` `int` `main() ` `{ ` `    ``// the edge list ` `    ``int` `edges[] = { { 1, 2 }, ` `                       ``{ 2, 3 }, ` `                       ``{ 1, 4 }, ` `                       ``{ 2, 4 } }; ` `    ``int` `len = ``sizeof``(edges) / (``sizeof``(``int``) * 2); ` ` `  `    ``// display the result ` `    ``cout << ``"sum = "` `<< count(edges, len) << endl; ` `    ``return` `0; ` `} `

## Java

 `// Java implementation for above approach ` `class` `GFG { ` ` `  `    ``// returns the sum of degree of all ` `    ``// the nodes in a undirected graph ` `    ``static` `int` `count(``int` `edges[][], ``int` `len) ` `    ``{ ` `        ``return` `2` `* len; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``// the edge list ` `        ``int` `edges[][] = { { ``1``, ``2` `}, ` `                          ``{ ``2``, ``3` `}, ` `                          ``{ ``1``, ``4` `}, ` `                          ``{ ``2``, ``4` `} }; ` `        ``int` `len = edges.length; ` ` `  `        ``// display the result ` `        ``System.out.println(``"sum = "` `+ count(edges, len)); ` `    ``} ` `} ` ` `  `// This code contributed by Rajput-Ji `

## Python 3

 `# Python3 implementation of above approach  ` ` `  `# returns the sum of degree of all  ` `# the nodes in a undirected graph  ` `def` `count(edges, length) : ` `     `  `    ``return` `2` `*` `length;  ` ` `  `# Driver Code ` `if` `__name__ ``=``=` `"__main__"` `:  ` ` `  `    ``# the edge list  ` `    ``edges ``=` `[[ ``1``, ``2` `],  ` `             ``[ ``2``, ``3` `],  ` `             ``[ ``1``, ``4` `],  ` `             ``[ ``2``, ``4` `]];  ` `    ``length ``=` `len``(edges); ` ` `  `    ``# display the result  ` `    ``print``(``"sum = "``, count(edges, length));  ` ` `  `# This code is contributed by Ryuga `

## C#

 `// C# implementation for above approach ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// returns the sum of degree of all ` `    ``// the nodes in a undirected graph ` `    ``static` `int` `count(``int``[, ] edges, ``int` `len) ` `    ``{ ` `        ``return` `2 * len; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``// the edge list ` `        ``int``[, ] edges = { { 1, 2 }, ` `                          ``{ 2, 3 }, ` `                          ``{ 1, 4 }, ` `                          ``{ 2, 4 } }; ` `        ``int` `len = edges.GetLength(0); ` ` `  `        ``// display the result ` `        ``Console.WriteLine(``"sum = "` `+ count(edges, len)); ` `    ``} ` `} ` ` `  `/* This code contributed by PrinciRaj1992 */`

## PHP

 ` `

Output:

`sum = 8`

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