Basic
https://www.geeksforgeeks.org/graph-and-its-representations/
// Array of Vector
// A simple representation of graph using STL
#include<bits/stdc++.h>
using namespace std;
// A utility function to add an edge in an
// undirected graph.
void addEdge(vector<int> adj[], int u, int v)
{
adj[u].push_back(v);
adj[v].push_back(u);
}
// A utility function to print the adjacency list
// representation of graph
void printGraph(vector<int> adj[], int V)
{
for (int v = 0; v < V; ++v)
{
cout << "\n Adjacency list of vertex "
<< v << "\n head ";
for (auto x : adj[v])
cout << "-> " << x;
printf("\n");
}
}
// Driver code
int main()
{
int V = 5;
vector<int> adj[V];
addEdge(adj, 0, 1);
addEdge(adj, 0, 4);
addEdge(adj, 1, 2);
addEdge(adj, 1, 3);
addEdge(adj, 1, 4);
addEdge(adj, 2, 3);
addEdge(adj, 3, 4);
printGraph(adj, V);
return 0;
}
// Vector of vector
// A utility function to add an edge in an
// undirected graph.
void addEdge(vector<vector<int> > &adj, int u, int v)
{
adj[u].push_back(v);
adj[v].push_back(u);
}
// A utility function to print the adjacency list
// representation of graph
void printGraph(vector<vector<int> > &adj, int V)
{
for (int v = 0; v < V; ++v)
{
cout << "\n Adjacency list of vertex "
<< v << "\n head ";
for (auto x : adj[v])
cout << "-> " << x;
printf("\n");
}
}
// Driver code
int main()
{
int V = 5;
vector<vector<int> > adj(V);
addEdge(adj, 0, 1);
addEdge(adj, 0, 4);
addEdge(adj, 1, 2);
addEdge(adj, 1, 3);
addEdge(adj, 1, 4);
addEdge(adj, 2, 3);
addEdge(adj, 3, 4);
printGraph(adj, V);
return 0;
}
https://www.geeksforgeeks.org/depth-first-search-or-dfs-for-a-graph/
// Array of List DFS Recursive
// C++ program to print DFS traversal from a given vertex in a given graph
#include<iostream>
#include<list>
using namespace std;
// Graph class represents a directed graph
// using adjacency list representation
class Graph
{
int V; // No. of vertices
// Pointer to an array containing
// adjacency lists
list<int> *adj;
// A recursive function used by DFS
void DFSUtil(int v, bool visited[]);
public:
Graph(int V); // Constructor
// function to add an edge to graph
void addEdge(int v, int w);
// DFS traversal of the vertices
// reachable from v
void DFS(int v);
};
Graph::Graph(int V)
{
this->V = V;
adj = new list<int>[V];
}
void Graph::addEdge(int v, int w)
{
adj[v].push_back(w); // Add w to v’s list.
}
void Graph::DFSUtil(int v, bool visited[])
{
// Mark the current node as visited and
// print it
visited[v] = true;
cout << v << " ";
// Recur for all the vertices adjacent
// to this vertex
list<int>::iterator i;
for (i = adj[v].begin(); i != adj[v].end(); ++i)
if (!visited[*i])
DFSUtil(*i, visited);
}
// DFS traversal of the vertices reachable from v.
// It uses recursive DFSUtil()
void Graph::DFS(int v)
{
// Mark all the vertices as not visited
bool *visited = new bool[V];
for (int i = 0; i < V; i++)
visited[i] = false;
// Call the recursive helper function
// to print DFS traversal
DFSUtil(v, visited);
}
int main()
{
// Create a graph given in the above diagram
Graph g(4);
g.addEdge(0, 1);
g.addEdge(0, 2);
g.addEdge(1, 2);
g.addEdge(2, 0);
g.addEdge(2, 3);
g.addEdge(3, 3);
cout << "Following is Depth First Traversal"
" (starting from vertex 2) \n";
g.DFS(2);
return 0;
}
BFS
https://www.geeksforgeeks.org/breadth-first-search-or-bfs-for-a-graph/
// Program to print BFS traversal from a given
// source vertex. BFS(int s) traverses vertices
// reachable from s.
#include<iostream>
#include <list>
using namespace std;
// This class represents a directed graph using
// adjacency list representation
class Graph
{
int V; // No. of vertices
// Pointer to an array containing adjacency
// lists
list<int> *adj;
public:
Graph(int V); // Constructor
// function to add an edge to graph
void addEdge(int v, int w);
// prints BFS traversal from a given source s
void BFS(int s);
};
Graph::Graph(int V)
{
this->V = V;
adj = new list<int>[V];
}
void Graph::addEdge(int v, int w)
{
adj[v].push_back(w); // Add w to v’s list.
}
void Graph::BFS(int s)
{
// Mark all the vertices as not visited
bool *visited = new bool[V];
for(int i = 0; i < V; i++)
visited[i] = false;
// Create a queue for BFS
list<int> queue;
// Mark the current node as visited and enqueue it
visited[s] = true;
queue.push_back(s);
// 'i' will be used to get all adjacent
// vertices of a vertex
list<int>::iterator i;
while(!queue.empty())
{
// Dequeue a vertex from queue and print it
s = queue.front();
cout << s << " ";
queue.pop_front();
// Get all adjacent vertices of the dequeued
// vertex s. If a adjacent has not been visited,
// then mark it visited and enqueue it
for (i = adj[s].begin(); i != adj[s].end(); ++i)
{
if (!visited[*i])
{
visited[*i] = true;
queue.push_back(*i);
}
}
}
}
// Driver program to test methods of graph class
int main()
{
// Create a graph given in the above diagram
Graph g(4);
g.addEdge(0, 1);
g.addEdge(0, 2);
g.addEdge(1, 2);
g.addEdge(2, 0);
g.addEdge(2, 3);
g.addEdge(3, 3);
cout << "Following is Breadth First Traversal "
<< "(starting from vertex 2) \n";
g.BFS(2);
return 0;
}
Graph implementation using STL for competitive programming | Set 1 (DFS of Unweighted and Undirected)
// A simple representation of graph using STL,
// for the purpose of competitive programming
#include<bits/stdc++.h>
using namespace std;
// A utility function to add an edge in an
// undirected graph.
void addEdge(vector<int> adj[], int u, int v)
{
adj[u].push_back(v);
adj[v].push_back(u);
}
// A utility function to do DFS of graph
// recursively from a given vertex u.
void DFSUtil(int u, vector<int> adj[],
vector<bool> &visited)
{
visited[u] = true;
cout << u << " ";
for (int i=0; i<adj[u].size(); i++)
if (visited[adj[u][i]] == false)
DFSUtil(adj[u][i], adj, visited);
}
// This function does DFSUtil() for all
// unvisited vertices.
void DFS(vector<int> adj[], int V)
{
vector<bool> visited(V, false);
for (int u=0; u<V; u++)
if (visited[u] == false)
DFSUtil(u, adj, visited);
}
// Driver code
int main()
{
int V = 5;
// The below line may not work on all
// compilers. If it does not work on
// your compiler, please replace it with
// following
// vector<int> *adj = new vector<int>[V];
vector<int> adj[V];
// Vertex numbers should be from 0 to 4.
addEdge(adj, 0, 1);
addEdge(adj, 0, 4);
addEdge(adj, 1, 2);
addEdge(adj, 1, 3);
addEdge(adj, 1, 4);
addEdge(adj, 2, 3);
addEdge(adj, 3, 4);
DFS(adj, V);
return 0;
}
Graph implementation using STL for competitive programming | Set 2 (Weighted graph)
#include <iostream>
#include <string>
#include <vector>
#include <stack> //?
#include <queue> //?
#include <map> // ?
#include <algorithm> // std::swap
#include <utility> // pair
using namespace std;
// To add an edge
void addEdge(vector <pair<int, int> > adj[], int u,
int v, int wt)
{
adj[u].push_back(make_pair(v, wt));
adj[v].push_back(make_pair(u, wt));
}
// Print adjacency list representaion ot graph
void printGraph(vector<pair<int,int> > adj[], int V)
{
int v, w;
for (int u = 0; u < V; u++)
{
std::cout << "Node " << u << " makes an edge with \n";
for (auto it = adj[u].begin(); it!=adj[u].end(); it++)
{
v = it->first;
w = it->second;
std::cout << "\tNode " << v << " with edge weight ="
<< w << "\n";
}
std::cout << "\n";
}
}
// Driver code
int main()
{
int V = 5;
vector<pair<int, int> > adj[V];
addEdge(adj, 0, 1, 10);
addEdge(adj, 0, 4, 20);
addEdge(adj, 1, 2, 30);
addEdge(adj, 1, 3, 40);
addEdge(adj, 1, 4, 50);
addEdge(adj, 2, 3, 60);
addEdge(adj, 3, 4, 70);
printGraph(adj, V);
return 0;
}