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# Minimum degree of three nodes forming a triangle in a given Graph

• Last Updated : 28 May, 2021

Given an undirected graph consisting of N vertices and M edges and an array edges[][], with each row representing two vertices connected by an edge, the task is to find the minimum degree of three nodes forming a triangle in the graph. If there doesn’t exist any triangle in the graph, then print “-1”.

Examples:

Input: N = 7, Edges = [[1, 2], [1, 3], [2, 3], [1, 4], [2, 5], [2, 7], [3, 6], [3, 7]]
Output: 4
Explanation: Below is the representation of the above graph:

There are two connected triangles:

1. One formed by nodes {1, 2, 3}. Degree of the triangle = 5.
2. Second triangle formed by nodes {2, 3, 7}. Degree of the triangle = 4.

The minimum degree is 4.

Input: N = 6, Edges = [[1, 2], [1, 3], [2, 3], [1, 6], [3, 4], [4, 5]]
Output: 2

Approach: The given problem can be solved by finding the degree of every triplet of nodes forming a triangle and count the degree of each node in that triangle. Follow the steps below to solve the problem:

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to find the minimum degree``// of a connected triangle in the graph``int` `minTrioDegree(``int` `N,``                  ``vector >& Edges)``{``    ``// Store the degree of each node``    ``// in the graph``    ``int` `degree[N + 1] = { 0 };` `    ``// Stores the representation of``    ``// graph in an adjancency matrix``    ``int` `adj[N + 1][N + 1] = { 0 };` `    ``// Create the adjacency matrix and``    ``// count the degree of nodes``    ``for` `(``int` `i = 0; i < Edges.size(); i++) {` `        ``// u & v are the endpoint of``        ``// the ith edge``        ``int` `u = Edges[i][0];``        ``int` `v = Edges[i][1];` `        ``// Mark both edges i.e.,``        ``// edge u->v and v->u``        ``adj[u][v] = adj[u][v] = 1;` `        ``// Increment degree by 1``        ``// of both endnodes``        ``degree[u]++;``        ``degree[v]++;``    ``}` `    ``// Stores the required result``    ``int` `ans = INT_MAX;` `    ``// Traverse for the first node``    ``for` `(``int` `i = 1; i <= N; i++) {` `        ``// Traverse for the second node``        ``for` `(``int` `j = i + 1; j <= N; j++) {` `            ``// If there is an edge between``            ``// these two nodes``            ``if` `(adj[i][j] == 1) {` `                ``// Traverse all possible``                ``// third nodes``                ``for` `(``int` `k = j + 1;``                     ``k <= N; k++) {` `                    ``// If there is an edge``                    ``// between third node``                    ``// and the previous two``                    ``if` `(adj[i][k] == 1``                        ``&& adj[j][k] == 1) {` `                        ``// Update ans``                        ``ans = min(ans,``                                  ``degree[i]``                                      ``+ degree[j]``                                      ``+ degree[k] - 6);``                    ``}``                ``}``            ``}``        ``}``    ``}` `    ``// Return the result``    ``return` `ans == INT_MAX ? -1 : ans;``}` `// Driver Code``int` `main()``{``    ``vector > Edges;``    ``Edges = { { 1, 2 }, { 1, 3 },``              ``{ 2, 3 }, { 1, 4 },``              ``{ 2, 5 }, { 2, 7 },``              ``{ 3, 6 }, { 3, 7 } };``    ``int` `N = 7;` `    ``cout << minTrioDegree(N, Edges);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.util.*;` `class` `GFG{` `// Function to find the minimum degree``// of a connected triangle in the graph``static` `int` `minTrioDegree(``int` `N,``int` `[][]Edges)``{``    ``// Store the degree of each node``    ``// in the graph``    ``int` `degree[] = ``new` `int``[N + ``1``];` `    ``// Stores the representation of``    ``// graph in an adjancency matrix``    ``int` `adj[][] = ``new` `int``[N + ``1``][N + ``1``];` `    ``// Create the adjacency matrix and``    ``// count the degree of nodes``    ``for` `(``int` `i = ``0``; i < Edges.length; i++) {` `        ``// u & v are the endpoint of``        ``// the ith edge``        ``int` `u = Edges[i][``0``];``        ``int` `v = Edges[i][``1``];` `        ``// Mark both edges i.e.,``        ``// edge u.v and v.u``        ``adj[u][v] = adj[u][v] = ``1``;` `        ``// Increment degree by 1``        ``// of both endnodes``        ``degree[u]++;``        ``degree[v]++;``    ``}` `    ``// Stores the required result``    ``int` `ans = Integer.MAX_VALUE;` `    ``// Traverse for the first node``    ``for` `(``int` `i = ``1``; i <= N; i++) {` `        ``// Traverse for the second node``        ``for` `(``int` `j = i + ``1``; j <= N; j++) {` `            ``// If there is an edge between``            ``// these two nodes``            ``if` `(adj[i][j] == ``1``) {` `                ``// Traverse all possible``                ``// third nodes``                ``for` `(``int` `k = j + ``1``;``                     ``k <= N; k++) {` `                    ``// If there is an edge``                    ``// between third node``                    ``// and the previous two``                    ``if` `(adj[i][k] == ``1``                        ``&& adj[j][k] == ``1``) {` `                        ``// Update ans``                        ``ans = Math.min(ans,``                                  ``degree[i]``                                      ``+ degree[j]``                                      ``+ degree[k] - ``6``);``                    ``}``                ``}``            ``}``        ``}``    ``}` `    ``// Return the result``    ``return` `ans == Integer.MAX_VALUE ? -``1` `: ans;``}` `// Driver Code``public` `static` `void` `main(String[] args)``{``    ``int` `[][]Edges = { { ``1``, ``2` `}, { ``1``, ``3` `},``              ``{ ``2``, ``3` `}, { ``1``, ``4` `},``              ``{ ``2``, ``5` `}, { ``2``, ``7` `},``              ``{ ``3``, ``6` `}, { ``3``, ``7` `} };``    ``int` `N = ``7``;` `    ``System.out.print(minTrioDegree(N, Edges));` `}``}` `// This code is contributed by 29AjayKumar`

## Python3

 `# Python3 program for the above approach``import` `sys` `# Function to find the minimum degree``# of a connected triangle in the graph``def` `minTrioDegree(N, Edges):` `    ``# Store the degree of each node``    ``# in the graph``    ``degree ``=` `[``0``] ``*` `(N``+``1``)` `    ``# Stores the representation of``    ``# graph in an adjancency matrix``    ``adj ``=` `[]` `    ``for` `i ``in` `range``(``0``, N``+``1``):``        ``temp ``=` `[]``        ``for` `j ``in` `range``(``0``, N``+``1``):``            ``temp.append(``0``)` `        ``adj.append(temp)` `    ``# Create the adjacency matrix and``    ``# count the degree of nodes``    ``for` `i ``in` `range``(``len``(Edges)):` `        ``# u & v are the endpoint of``        ``# the ith edge``        ``u ``=` `Edges[i][``0``]``        ``v ``=` `Edges[i][``1``]``        ` `        ``# Mark both edges i.e.,``        ``# edge u->v and v->u``        ``adj[u][v] ``=` `adj[u][v] ``=` `1` `        ``# Increment degree by 1``        ``# of both endnodes``        ``degree[u] ``+``=` `1``        ``degree[v] ``+``=` `1` `    ``# Stores the required result``    ``ans ``=` `sys.maxsize` `    ``# Traverse for the first node``    ``for` `i ``in` `range``(``1``, N``+``1``, ``1``):` `        ``# Traverse for the second node``        ``for` `j ``in` `range``(i ``+` `1``, N``+``1``, ``1``):` `            ``# If there is an edge between``            ``# these two nodes``            ``if` `adj[i][j] ``=``=` `1``:` `                ``# Traverse all possible``                ``# third nodes``                ``for` `k ``in` `range``(j ``+` `1``, N``+``1``, ``1``):` `                    ``# If there is an edge``                    ``# between third node``                    ``# and the previous two``                    ``if` `(adj[i][k] ``=``=` `1``) ``and` `(adj[j][k] ``=``=` `1``):` `                        ``# Update ans``                        ``ans ``=` `min``(ans, degree[i] ``+` `degree[j] ``+` `degree[k] ``-` `6``)` `    ``# Return the result``    ``if` `ans ``=``=` `sys.maxsize:``        ``return` `-``1``    ``return` `ans` `# Driver Code``Edges ``=` `[[``1``, ``2``], [``1``, ``3``], [``2``, ``3``], [``1``, ``4``], [``2``, ``5``], [``2``, ``7``], [``3``, ``6``], [``3``, ``7``]]``N ``=` `7` `print``(minTrioDegree(N, Edges))` `# This code is contributed by Dharanendra L V.`

## C#

 `// C# program for the above approach``using` `System;``using` `System.Collections.Generic;``public` `class` `GFG``{` `// Function to find the minimum degree``// of a connected triangle in the graph``static` `int` `minTrioDegree(``int` `N, ``int` `[,]Edges)``{``  ` `    ``// Store the degree of each node``    ``// in the graph``    ``int` `[]degree = ``new` `int``[N + 1];` `    ``// Stores the representation of``    ``// graph in an adjancency matrix``    ``int` `[,]adj = ``new` `int``[N + 1, N + 1];` `    ``// Create the adjacency matrix and``    ``// count the degree of nodes``    ``for` `(``int` `i = 0; i < Edges.GetLength(0); i++)``    ``{` `        ``// u & v are the endpoint of``        ``// the ith edge``        ``int` `u = Edges[i, 0];``        ``int` `v = Edges[i, 1];` `        ``// Mark both edges i.e.,``        ``// edge u.v and v.u``        ``adj[u, v] = adj[u, v] = 1;` `        ``// Increment degree by 1``        ``// of both endnodes``        ``degree[u]++;``        ``degree[v]++;``    ``}` `    ``// Stores the required result``    ``int` `ans = ``int``.MaxValue;` `    ``// Traverse for the first node``    ``for` `(``int` `i = 1; i <= N; i++) {` `        ``// Traverse for the second node``        ``for` `(``int` `j = i + 1; j <= N; j++) {` `            ``// If there is an edge between``            ``// these two nodes``            ``if` `(adj[i,j] == 1) {` `                ``// Traverse all possible``                ``// third nodes``                ``for` `(``int` `k = j + 1;``                     ``k <= N; k++) {` `                    ``// If there is an edge``                    ``// between third node``                    ``// and the previous two``                    ``if` `(adj[i,k] == 1``                        ``&& adj[j,k] == 1) {` `                        ``// Update ans``                        ``ans = Math.Min(ans,``                                  ``degree[i]``                                      ``+ degree[j]``                                      ``+ degree[k] - 6);``                    ``}``                ``}``            ``}``        ``}``    ``}` `    ``// Return the result``    ``return` `ans == ``int``.MaxValue ? -1 : ans;``}` `// Driver Code``public` `static` `void` `Main(String[] args)``{``    ``int` `[,]Edges = { { 1, 2 }, { 1, 3 },``              ``{ 2, 3 }, { 1, 4 },``              ``{ 2, 5 }, { 2, 7 },``              ``{ 3, 6 }, { 3, 7 } };``    ``int` `N = 7;` `    ``Console.Write(minTrioDegree(N, Edges));``}``}` `// This code is contributed by 29AjayKumar`

## Javascript

 ``
Output:
`4`

Time Complexity: O(N3
Auxiliary Space: O(N2)

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