Graph

#include <iostream>

#include <list>

#include <vector>

using namespace std;

//define a graph

class Graph {

    // variable

    int V; // number of vertex in a graph

    list <int> *adj;  // the adjacency lists of a vertex

public:

    // constructor

    Graph(int nVetex)

        V = nVetex;

        adj = new list<int>[nVetex];

    // destructor

    ~Graph()

        // nothing

    //function

    void addEdge(int start, int end)

        adj[start].push_back(end);

    void displayArray(vector<bool> &visit)

        for(int i=0; i<visit.size();i++)

            cout<< visit[i]<<",";

        cout<<endl;

    void displayList(list<int> & ls)

        cout<<"Display a List:";

        list<int>::iterator i;

        for(i = ls.begin(); i!=ls.end();++i)

            cout<<*i<<endl;

    void BFS(int start)

        list <int> workq;

        // use a temporary array to save the visiting information

        vector <bool> Visit(this->V);

        for (int i=0; i<this->V; i++)

            Visit[i] = false;

        //first add the start node to the workq

        Visit[start] = true;

        workq.push_back(start);

        while(!workq.empty())

            // look for the other nodes in the graph

            int current_node = workq.front();

            workq.pop_front();

            list<int> t = this->adj[current_node];

            int n = t.size();

            cout<<current_node<<" has "<<n<<" neibour nodes"<<endl;

            displayList(t);

            displayArray(Visit);

            for(int k =0; k<n; k++)

                int nex = t.front();

                t.pop_front();

                cout<< nex<<","<<Visit[nex]<<endl;

                if(Visit[nex] != true)

                { // if not visited before, add it to the workq

                    cout<<"go here"<<endl;

                    Visit[nex] = true;

                    workq.push_back(nex);

            displayArray(Visit);

            cout<<"done for node"<<current_node<<endl;

    void DFSUltus(int start, vector<bool> & Visit)

        Visit[start] = true;

        cout<<start<<endl;

        list<int>::iterator i;

        for(i=adj[start].begin();i!=adj[start].end();i++)

            if(Visit[*i] == false)

                DFSUltus(*i,Visit);

    void DFS(int start)

        vector<bool> Visit(this->V);

        for(int i=0; i<Visit.size();i++)

            Visit[i] = false;

        DFSUltus(start, Visit);

};

// main function for breadth first search

int main()

    // construct a graph

    Graph G(6);

    G.addEdge(0,3);

    G.addEdge(1,3);

    G.addEdge(1,2);

    G.addEdge(1,4);

    G.addEdge(2,5);

    G.addEdge(3,5);

    G.addEdge(5,3);

    G.addEdge(3,1);

    // BFS

    //G.BFS(2);

    G.DFS(2);

Dijkstra algorithm for searching the shortest path in a graph

The following code is copied from GeeksforGeeks

// A C++ program for Dijkstra's single source shortest path algorithm.

// The program is for adjacency matrix representation of the graph

#include <stdio.h>

#include <limits.h>

// Number of vertices in the graph

#define V 9

// A utility function to find the vertex with minimum distance value, from

// the set of vertices not yet included in shortest path tree

int minDistance(int dist[], bool sptSet[])

{

// Initialize min value

int min = INT_MAX, min_index;

for (int v = 0; v < V; v++)

if (sptSet[v] == false && dist[v] <= min)

min = dist[v], min_index = v;

return min_index;

}

// A utility function to print the constructed distance array

int printSolution(int dist[], int n)

{

printf("Vertex Distance from Source\n");

for (int i = 0; i < V; i++)

printf("%d tt %d\n", i, dist[i]);

}

// Function that implements Dijkstra's single source shortest path algorithm

// for a graph represented using adjacency matrix representation

void dijkstra(int graph[V][V], int src)

{

int dist[V]; // The output array. dist[i] will hold the shortest

// distance from src to i

bool sptSet[V]; // sptSet[i] will true if vertex i is included in shortest

// path tree or shortest distance from src to i is finalized

// Initialize all distances as INFINITE and stpSet[] as false

for (int i = 0; i < V; i++)

dist[i] = INT_MAX, sptSet[i] = false;

// Distance of source vertex from itself is always 0

dist[src] = 0;

// Find shortest path for all vertices

for (int count = 0; count < V-1; count++)

{

// Pick the minimum distance vertex from the set of vertices not

// yet processed. u is always equal to src in the first iteration.

int u = minDistance(dist, sptSet);

// Mark the picked vertex as processed

sptSet[u] = true;

// Update dist value of the adjacent vertices of the picked vertex.

for (int v = 0; v < V; v++)

// Update dist[v] only if is not in sptSet, there is an edge from

// u to v, and total weight of path from src to v through u is

// smaller than current value of dist[v]

if (!sptSet[v] && graph[u][v] && dist[u] != INT_MAX

&& dist[u]+graph[u][v] < dist[v])

dist[v] = dist[u] + graph[u][v];

}

// print the constructed distance array

printSolution(dist, V);

}

// driver program to test above function

int main()

{

/* Let us create the example graph discussed above */

int graph[V][V] = {{0, 4, 0, 0, 0, 0, 0, 8, 0},

{4, 0, 8, 0, 0, 0, 0, 11, 0},

{0, 8, 0, 7, 0, 4, 0, 0, 2},

{0, 0, 7, 0, 9, 14, 0, 0, 0},

{0, 0, 0, 9, 0, 10, 0, 0, 0},

{0, 0, 4, 14, 10, 0, 2, 0, 0},

{0, 0, 0, 0, 0, 2, 0, 1, 6},

{8, 11, 0, 0, 0, 0, 1, 0, 7},

{0, 0, 2, 0, 0, 0, 6, 7, 0}

};

dijkstra(graph, 0);

return 0;

}

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