# C++ Program to Represent Graph Using 2D Arrays

This is a C++ program represents a graph using 2D arrays.

The time complexity of this algorithm is O(v*v).

## Algorithm

Begin
Take the input of the number of vertex ‘v’ and edges ‘e’.
Assign memory to the graph[][] matrix.
Take the input of ‘e’ pairs of vertexes of the given graph in graph[][].
For each pair of connected vertex(v1, v2), store 1 in the graph[][] at the index (v1, v2) and (v2, v1).
Print the matrix using PrintMatrix().
End

## Example Code

#include<iostream>
#include<iomanip>
using namespace std;
void PrintMatrix(int **matrix, int n) {
int i, j;
cout<<"\n\n"<<setw(4)<<"";
for(i = 0; i < n; i++)
cout<<setw(3)<<"("<<i+1<<")";
cout<<"\n\n";
for(i = 0; i < n; i++) {
cout<<setw(3)<<"("<<i+1<<")";
for(j = 0; j < n; j++) {
cout<<setw(4)<<matrix[i][j];
}
cout<<"\n\n";
}
}
int main() {
int i, v, e, j, v1, v2;
cout<<"Enter the number of vertexes of the graph: ";
cin>>v;
int **graph;
graph = new int*[v];
for(i = 0; i < v; i++) {
graph[i] = new int[v];
for(j = 0; j < v; j++) graph[i][j] = 0;
}
cout<<"\nEnter the number of edges of the graph: ";
cin>>e;
for(i = 0; i < e; i++) {
cout<<"\nEnter the vertex pair for edge "<<i+1;
cout<<"\nV(1): ";
cin>>v1;
cout<<"V(2): ";
cin>>v2;
graph[v1-1][v2-1] = 1;
graph[v2-1][v1-1] = 1;
}
PrintMatrix(graph, v);
}

## Output

Enter the number of vertexes of the graph: 5
Enter the number of edges of the graph: 4
Enter the vertex pair for edge 1
V(1): 2
V(2): 1
Enter the vertex pair for edge 2
V(1): 3
V(2): 2
Enter the vertex pair for edge 3
V(1): 1
V(2): 1
Enter the vertex pair for edge 4
V(1): 3
V(2): 1
(1) (2) (3) (4) (5)
(1) 1 1 1 0 0
(2) 1 0 1 0 0
(3) 1 1 0 0 0
(4) 0 0 0 0 0
(5) 0 0 0 0 0