This is a C++ program to generate a graph for a given fixed degree sequence. This algorithm generates a undirected graph for the given degree sequence.It does not include self-edge and multiple edges.
Examples:
Input : degrees[] = {2, 2, 1, 1} Output : (0) (1) (2) (3) (0) 0 1 1 0 (1) 1 0 0 1 (2) 1 0 0 0 (3) 0 1 0 0 Explanation : We are given that there are four vertices with degree of vertex 0 as 2, degree of vertex 1 as 2, degree of vertex 2 as 1 and degree of vertex 3 as 1. Following is graph that follows given conditions. (0)----------(1) | | | | | | (2) (3)
Approach :
- Take the input of the number of vertexes and their corresponding degree.
- Declare adjacency matrix, mat[ ][ ] to store the graph.
- To create the graph, create the first loop to connect each vertex ‘i’.
- Second nested loop to connect the vertex ‘i’ to the every valid vertex ‘j’, next to it.
- If the degree of vertex ‘i’ and ‘j’ are more than zero then connect them.
- Print the adjacency matrix.
Based on the above explanation, below are implementations:
C++
// C++ program to generate a graph for a // given fixed degrees #include <bits/stdc++.h> using namespace std;
// A function to print the adjacency matrix. void printMat( int degseq[], int n)
{ // n is number of vertices
int mat[n][n];
memset (mat, 0, sizeof (mat));
for ( int i = 0; i < n; i++) {
for ( int j = i + 1; j < n; j++) {
// For each pair of vertex decrement
// the degree of both vertex.
if (degseq[i] > 0 && degseq[j] > 0) {
degseq[i]--;
degseq[j]--;
mat[i][j] = 1;
mat[j][i] = 1;
}
}
}
// Print the result in specified format
cout << "\n"
<< setw(3) << " " ;
for ( int i = 0; i < n; i++)
cout << setw(3) << "(" << i << ")" ;
cout << "\n\n" ;
for ( int i = 0; i < n; i++) {
cout << setw(4) << "(" << i << ")" ;
for ( int j = 0; j < n; j++)
cout << setw(5) << mat[i][j];
cout << "\n" ;
}
} // driver program to test above function int main()
{ int degseq[] = { 2, 2, 1, 1, 1 };
int n = sizeof (degseq) / sizeof (degseq[0]);
printMat(degseq, n);
return 0;
} |
Java
// Java program to generate a graph for a // given fixed degrees import java.util.*;
class GFG
{ // A function to print the adjacency matrix. static void printMat( int degseq[], int n)
{ // n is number of vertices
int [][]mat = new int [n][n];
for ( int i = 0 ; i < n; i++)
{
for ( int j = i + 1 ; j < n; j++)
{
// For each pair of vertex decrement
// the degree of both vertex.
if (degseq[i] > 0 && degseq[j] > 0 )
{
degseq[i]--;
degseq[j]--;
mat[i][j] = 1 ;
mat[j][i] = 1 ;
}
}
}
// Print the result in specified format
System.out.print( "\n" + setw( 3 ) + " " );
for ( int i = 0 ; i < n; i++)
System.out.print(setw( 3 ) + "(" + i + ")" );
System.out.print( "\n\n" );
for ( int i = 0 ; i < n; i++)
{
System.out.print(setw( 4 ) + "(" + i + ")" );
for ( int j = 0 ; j < n; j++)
System.out.print(setw( 5 ) + mat[i][j]);
System.out.print( "\n" );
}
} static String setw( int n)
{ String space = "" ;
while (n-- > 0 )
space += " " ;
return space;
} // Driver Code public static void main(String[] args)
{ int degseq[] = { 2 , 2 , 1 , 1 , 1 };
int n = degseq.length;
printMat(degseq, n);
} } // This code is contributed by 29AjayKumar |
Python3
# Python3 program to generate a graph # for a given fixed degrees # A function to print the adjacency matrix. def printMat(degseq, n):
# n is number of vertices
mat = [[ 0 ] * n for i in range (n)]
for i in range (n):
for j in range (i + 1 , n):
# For each pair of vertex decrement
# the degree of both vertex.
if (degseq[i] > 0 and degseq[j] > 0 ):
degseq[i] - = 1
degseq[j] - = 1
mat[i][j] = 1
mat[j][i] = 1
# Print the result in specified form
print ( " " , end = " " )
for i in range (n):
print ( " " , "(" , i, ")" , end = "")
print ()
print ()
for i in range (n):
print ( " " , "(" , i, ")" , end = "")
for j in range (n):
print ( " " , mat[i][j], end = "")
print ()
# Driver Code if __name__ = = '__main__' :
degseq = [ 2 , 2 , 1 , 1 , 1 ]
n = len (degseq)
printMat(degseq, n)
# This code is contributed by PranchalK |
C#
// C# program to generate a graph for a // given fixed degrees using System;
class GFG
{ // A function to print the adjacency matrix. static void printMat( int []degseq, int n)
{ // n is number of vertices
int [,]mat = new int [n, n];
for ( int i = 0; i < n; i++)
{
for ( int j = i + 1; j < n; j++)
{
// For each pair of vertex decrement
// the degree of both vertex.
if (degseq[i] > 0 && degseq[j] > 0)
{
degseq[i]--;
degseq[j]--;
mat[i, j] = 1;
mat[j, i] = 1;
}
}
}
// Print the result in specified format
Console.Write( "\n" + setw(3) + " " );
for ( int i = 0; i < n; i++)
Console.Write(setw(3) + "(" + i + ")" );
Console.Write( "\n\n" );
for ( int i = 0; i < n; i++)
{
Console.Write(setw(4) + "(" + i + ")" );
for ( int j = 0; j < n; j++)
Console.Write(setw(5) + mat[i, j]);
Console.Write( "\n" );
}
} static String setw( int n)
{ String space = "" ;
while (n-- > 0)
space += " " ;
return space;
} // Driver Code public static void Main(String[] args)
{ int []degseq = { 2, 2, 1, 1, 1 };
int n = degseq.Length;
printMat(degseq, n);
} } // This code is contributed by Princi Singh |
Javascript
<script> // JavaScript program to generate a graph for a // given fixed degrees // A function to print the adjacency matrix. function printMat(degseq,n)
{ // n is number of vertices
let mat = new Array(n);
for (let i=0;i<n;i++)
{
mat[i]= new Array(n);
for (let j=0;j<n;j++)
mat[i][j]=0;
}
for (let i = 0; i < n; i++)
{
for (let j = i + 1; j < n; j++)
{
// For each pair of vertex decrement
// the degree of both vertex.
if (degseq[i] > 0 && degseq[j] > 0)
{
degseq[i]--;
degseq[j]--;
mat[i][j] = 1;
mat[j][i] = 1;
}
}
}
// Print the result in specified format
document.write( "<br>" + setw(3) + " " );
for (let i = 0; i < n; i++)
document.write(setw(3) + "(" + i + ")" );
document.write( "<br><br>" );
for (let i = 0; i < n; i++)
{
document.write(setw(4) + "(" + i + ")" );
for (let j = 0; j < n; j++)
document.write(setw(5) + mat[i][j]);
document.write( "<br>" );
}
} function setw(n)
{ let space = "" ;
while (n-- > 0)
space += " " ;
return space;
} // Driver Code let degseq=[2, 2, 1, 1, 1]; let n = degseq.length; printMat(degseq, n); // This code is contributed by rag2127 </script> |
Output
(0) (1) (2) (3) (4) (0) 0 1 1 0 0 (1) 1 0 0 1 0 (2) 1 0 0 0 0 (3) 0 1 0 0 0 (4) 0 0 0 0 0
Time Complexity: O(v*v).
Space complexity : O(n^2) because it creates a 2-dimensional array (matrix) of size n * n, where n is the number of vertices in the graph.
Recommended Articles