aoa/graphColorBacktrack.c at master · undergradhub/aoa · GitHub

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#include<stdio.h>

static int m, n, c=0, count=0;
int g[50][50], x[50];

void nextValue(int k);
void GraphColoring(int k);

void main()
{
	int i, j, temp;

	printf("\nEnter the number of nodes: " );
	scanf("%d", &n);

	printf("\nEnter Adjacency Matrix:\n");

	for(i=1;i<=n;i++)
	{
		for(j=1;j<=n;j++)
			scanf("%d", &g[i][j]);
	}

	printf("\nPossible Solutions are\n");

	for(m=1;m<=n;m++)
	{
		if(c==1)
			break;
		GraphColoring(1);
	}

	printf("\nThe chromatic number is %d", m-1);

	//in for loop, m gets incremented first and then the condition is checked
	//so it is m minus 1

	printf("\nThe total number of solutions is %d", count);
}

void GraphColoring(int k)
{
	int i;

	while(1)
	{
		nextValue(k);
		if(x[k]==0)
			return;

		if(k==n)
		{
			c=1;
			for(i=1;i<=n;i++)
				printf("%d ", x[i]);
			count++;
			printf("\n");
		}
		else
			GraphColoring(k+1);
	}
}

void nextValue(int k)
{
	int j;

	while(1)
	{
		x[k]=(x[k]+1)%(m+1);
		if(x[k]==0)
			return;

		for(j=1;j<=n;j++)
		{
			if(g[k][j]==1&&x[k]==x[j])
				break;
		}

		if(j==(n+1))
			return;
	}
}