# Check for transitive property in a given Undirected Graph

Given an undirected graph **G** with vertices numbered in the range **[1, N]** and an array **Edges[][]** consisting of **M** edges, the task is to check if all triplets of the undirected graph satisfies the transitive property or not. If found to be true, then print **“YES”**. Otherwise, print **“NO”**.

Transitive property of an undirected graph states that:

If vertexXis connected to vertexY, vertexYis connected to vertexZ, then vertexXmust be connected to the vertexZ.

**Examples:**

Input:N = 4, M = 3 Edges[] = {{1, 3}, {3, 4}, {1, 4}}Output:YESExplanation:

Input :N = 4, M = 4, Edges[] = {{3, 1}, {2, 3}, {3, 4}, {1, 2}}Output: NOExplanation:

**Naive Approach:** The simplest approach to solve the above problem is to traverse over every** triplet** of vertices** (i, j, k)**, and for each such triplet, check if there is an edge between vertices **j** and **k** if** i **and** j**, and** i** and **k** are directly connected by an edge with the help of an adjacency matrix.

**Time Complexity:** O(N^{3})**Auxiliary Space:** O(N^{2})

**Efficient Approach: **The idea is to find all the connected components present in the graph. Finally, check if all the connected components of the graph are a complete graph or not. If found to be true, then print **“YES”**. Otherwise, print **“NO”**. Follow the steps below to solve the problem:

- Represent the graph,
**G**in the form of adjacency list. - Find all the connected components of the graph and check if the connected component is a complete graph or not by performing the following operations:
- Find total count of vertices in the current connected graph say,
**X**. - If all the vertices of the connected component are not connected to
**X – 1**vertices, then print**“NO”**.

- Find total count of vertices in the current connected graph say,
- Finally, check if all the connected components are a complete graph or not. IF found to be true, then print
**“YES”**.

Below is the implementation of the above approach:

## C++

`// C++ program of the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Stores undirected graph using` `// adjacency list representation` `class` `Graph {` ` ` `// Stores count of vertices` ` ` `int` `V;` ` ` `// adj[i]: Store all the nodes` ` ` `// connected to i` ` ` `list<` `int` `>* adj;` ` ` `// DFS function` ` ` `void` `DFSUtil(` `int` `v, ` `bool` `visited[], ` `int` `id[],` ` ` `int` `id_number, ` `int` `& c);` `public` `:` ` ` `Graph(` `int` `V);` ` ` `~Graph();` ` ` `// Connect two vertices v and w` ` ` `void` `addEdge(` `int` `v, ` `int` `w);` ` ` `// Check if the connected component` ` ` `// is a complete graph or not` ` ` `bool` `connectedComponents();` `};` `Graph::Graph(` `int` `V)` `{` ` ` `this` `->V = V;` ` ` `adj = ` `new` `list<` `int` `>[V + 1];` `}` `// Destructor` `Graph::~Graph() { ` `delete` `[] adj; }` `// Function to add an undirected` `// edge between two vertices` `void` `Graph::addEdge(` `int` `v, ` `int` `w)` `{` ` ` `adj[v].push_back(w);` ` ` `adj[w].push_back(v);` `}` `// Function to find all the connected` `// components of a graph using DFS` `void` `Graph::DFSUtil(` `int` `v, ` `bool` `visited[], ` `int` `id[],` ` ` `int` `id_number, ` `int` `& c)` `{` ` ` `// Mark the vertex v as visited` ` ` `visited[v] = ` `true` `;` ` ` `// Assign an id of current` ` ` `// connected component` ` ` `id[v] = id_number;` ` ` `// Increase the count of vertices in` ` ` `// current connected component` ` ` `c++;` ` ` `// Recursively call for all the` ` ` `// vertices adjacent to this vertex` ` ` `list<` `int` `>::iterator i;` ` ` `// Iterate over all the adjacent` ` ` `// vertices of the current vertex` ` ` `for` `(i = adj[v].begin(); i != adj[v].end();` ` ` `++i) {` ` ` `// If current vertex is not visited` ` ` `if` `(!visited[*i])` ` ` `DFSUtil(*i, visited, id,` ` ` `id_number, c);` ` ` `}` `}` `// Function to find connected` `// components of the graph` `bool` `Graph::connectedComponents()` `{` ` ` `bool` `* visited = ` `new` `bool` `[V + 1];` ` ` `// id[i]: Stores an unique id of connected` ` ` `// component in which vertex i exists` ` ` `int` `* id = ` `new` `int` `[V + 1];` ` ` `// Store count of nodes in current` ` ` `// connected component` ` ` `int` `* component_size = ` `new` `int` `[V + 1];` ` ` `// Mark all the vertices as not visited` ` ` `for` `(` `int` `v = 1; v <= V; v++)` ` ` `visited[v] = ` `false` `;` ` ` `for` `(` `int` `v = 1; v <= V; v++) {` ` ` `// If vertex v is not marked` ` ` `if` `(visited[v] == ` `false` `) {` ` ` `// Stores the size of a component` ` ` `// in which vertex v lies` ` ` `int` `c = 0;` ` ` `// Stores id of current` ` ` `// connected component` ` ` `int` `id_number = v;` ` ` `DFSUtil(v, visited, id,` ` ` `id_number, c);` ` ` `// Stores count of vertices of` ` ` `// current component` ` ` `component_size[v] = c;` ` ` `}` ` ` `else` `{` ` ` `component_size[v]` ` ` `= component_size[id[v]];` ` ` `}` ` ` `}` ` ` `// Iterate over all the vertices` ` ` `for` `(` `int` `v = 1; v <= V; v++) {` ` ` `// IF connected component[v] is` ` ` `// not a complete graph` ` ` `if` `(component_size[v] - 1` ` ` `!= (` `int` `)adj[v].size()) {` ` ` `delete` `[] visited;` ` ` `return` `false` `;` ` ` `}` ` ` `}` ` ` `delete` `[] visited;` ` ` `return` `true` `;` `}` `// Function to check if graph is` `// Edge Transitive or not` `void` `isTransitive(` `int` `N, ` `int` `M,` ` ` `vector<vector<` `int` `> > Edge)` `{` ` ` `// Initialize a graph` ` ` `Graph G(N);` ` ` `// Traverse the array Edge[]` ` ` `for` `(` `int` `i = 0; i < M; i++) {` ` ` `G.addEdge(Edge[i][0], Edge[i][1]);` ` ` `}` ` ` `// If all the connected components` ` ` `// are a complete graph` ` ` `int` `f = G.connectedComponents();` ` ` `if` `(f == 0) {` ` ` `cout << ` `"NO\n"` `;` ` ` `}` ` ` `else` `{` ` ` `cout << ` `"YES\n"` `;` ` ` `}` `}` `// Driver Code` `int` `main()` `{` ` ` `// Input` ` ` `int` `N = 4, M = 3;` ` ` `vector<vector<` `int` `> > Edge{ { 1, 3 },` ` ` `{ 3, 4 },` ` ` `{ 1, 4 } };` ` ` `isTransitive(N, M, Edge);` ` ` `return` `0;` `}` |

## Python3

`# Python3 program of the above approach` `# Function to add an undirected` `# edge between two vertices` `def` `addEdge(v, w):` ` ` `global` `adj` ` ` `adj[v].append(w)` ` ` `adj[w].append(v)` `# Function to find all the connected` `# components of a graph using DFS` `def` `DFSUtil(v, ` `id` `, id_number):` ` ` `global` `visited, adj, c` ` ` `# Mark the vertex v as visited` ` ` `visited[v] ` `=` `True` ` ` `# Assign an id of current` ` ` `# connected component` ` ` `id` `[v] ` `=` `id_number` ` ` `# Increase the count of vertices in` ` ` `# current connected component` ` ` `c ` `+` `=` `1` ` ` `# Iterate over all the adjacent` ` ` `# vertices of the current vertex` ` ` `for` `i ` `in` `adj[v]:` ` ` ` ` `# If current vertex is not visited` ` ` `if` `(` `not` `visited[i]):` ` ` `DFSUtil(i, ` `id` `, id_number)` `# Function to find connected` `# components of the graph` `def` `connectedComponents():` ` ` `global` `V, adj, visited, c` ` ` `# id[i]: Stores an unique id of connected` ` ` `# component in which vertex i exists` ` ` `id` `=` `[` `0` `]` `*` `(V ` `+` `1` `)` ` ` `# Store count of nodes in current` ` ` `# connected component` ` ` `component_size ` `=` `[` `0` `]` `*` `(V ` `+` `1` `)` ` ` `for` `v ` `in` `range` `(` `1` `, V ` `+` `1` `):` ` ` `# If vertex v is not marked` ` ` `if` `(visited[v] ` `=` `=` `False` `):` ` ` `# Stores the size of a component` ` ` `# in which vertex v lies` ` ` `c ` `=` `0` ` ` `# Stores id of current` ` ` `# connected component` ` ` `id_number ` `=` `v` ` ` `DFSUtil(v, ` `id` `, id_number)` ` ` `# Stores count of vertices of` ` ` `# current component` ` ` `component_size[v] ` `=` `c` ` ` `else` `:` ` ` `component_size[v] ` `=` `component_size[` `id` `[v]]` ` ` `# Iterate over all the vertices` ` ` `for` `v ` `in` `range` `(` `1` `, V ` `+` `1` `):` ` ` `# IF connected component[v] is` ` ` `# not a complete graph` ` ` `if` `(component_size[v] ` `-` `1` `!` `=` `len` `(adj[v])):` ` ` `return` `False` ` ` `return` `True` `# Function to check if graph is` `# Edge Transitive or not` `def` `isTransitive(N, M, Edge):` ` ` `global` `adj, visited, c` ` ` `# Traverse the array Edge[]` ` ` `for` `i ` `in` `range` `(M):` ` ` `addEdge(Edge[i][` `0` `], Edge[i][` `1` `])` ` ` `# If all the connected components` ` ` `# are a complete graph` ` ` `f ` `=` `connectedComponents()` ` ` `if` `(f ` `=` `=` `0` `):` ` ` `print` `(` `"NO"` `)` ` ` `else` `:` ` ` `print` `(` `"YES"` `)` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` ` ` `# Input` ` ` `V, c ` `=` `5` `, ` `0` ` ` `adj ` `=` `[[] ` `for` `i ` `in` `range` `(V ` `+` `1` `)]` ` ` `visited ` `=` `[` `False` `] ` `*` `(V ` `+` `1` `)` ` ` `N, M ` `=` `4` `, ` `3` ` ` `Edge ` `=` `[ [ ` `1` `, ` `3` `],` ` ` `[ ` `3` `, ` `4` `],` ` ` `[ ` `1` `, ` `4` `] ]` ` ` `isTransitive(N, M, Edge)` ` ` `# This code is contributed by mohit kumar 29` |

**Output:**

YES

**Time Complexity:** O(N + M)**Auxiliary Space:** O(N^{2})