This is a java program to check graph construction is possible or not using given degree sequence. If the sum of degree is even graph construction is possible, not otherwise.

Here is the source code of the Java Program to Check if any Graph is Possible to be Constructed for a Given Degree Sequence. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

package com.sanfoundry.combinatorial;

import java.util.ArrayList;

import java.util.List;

import java.util.Scanner;

public class CheckGraphConstuction

`{`

public static Integer sum(List<Integer> list)

`{`

Integer sum = 0;

for (Integer integer : list)

`{`

sum += integer;

`}`

return sum;

`}`

public static void main(String[] args)

`{`

Scanner sc = new Scanner(System.in);

System.out.println("Enter the number of vertices: ");

Integer n = sc.nextInt();

System.out

.println("Enter the Degree Sequence: <Degree sequence is always in non-increasing order>");

List<Integer> sequence = new ArrayList<Integer>();

while (n > 0)

`{`

sequence.add(sc.nextInt());

`n--;`

`}`

System.out.println(sequence.toString());

if (sum(sequence) % 2 == 0)

`{`

System.out

.println("Graph can be constructed using the given sequence G=("

+ sequence.size()

+ ", "

+ (sum(sequence) / 2)

+ ").");

`}`

sc.close();

`}`

`}`

Output:

$ javac CheckGraphConstuction.java $ java CheckGraphConstuction Enter the number of vertices: 7 Enter the Degree Sequence: <Degree sequence is always in non-increasing order> 5 3 3 2 2 1 0 [5, 3, 3, 2, 2, 1, 0] Graph can be constructed using the given sequence G=(7, 8). Enter the number of vertices: 3 Enter the Degree Sequence: <Degree sequence is always in non-increasing order> 3 3 1 [3, 3, 1] no soultion exists.

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