optimal.c

#include <stdio.h>

int main()
{	
	int pages[20], frames[20], np, nf, i, j, faults = 0, q ,k, temp[20];

	int flag1, flag2, flag3, pos, max;

	printf("Enter the no. of frames-\n");
	scanf("%d", &nf);

	printf("Enter the no. of pages-\n");
	scanf("%d", &np);

	printf("Enter the pages -\n");
	for(i=0;i<np;i++)
		scanf("%d", &pages[i]);

	for(i=0;i<20;i++)
		frames[i] = -1;

	for(i=0; i<np; i++)
	{
		flag1 = 0;
		flag2 = 0;

		for(j=0; j<nf; j++)
		{
			if(frames[j] == pages[i])
			{
				flag1 = flag2 = 1;
				break;
			}
		}

		if(flag1 == 0)
		{
			for(j=0; j<nf; j++){
			if(frames[j] == -1)
			{
				faults++;
				frames[j] = pages[i];
				flag2 = 1;
				break;
			}
			}

		}//flag1

		if(flag2 == 0)
		{
			flag3 = 0;

			for(j=0;j<nf;j++)
			{
				temp[j] = -1;

				for(k = i+1; k < np; k++)
				{
					if(frames[j] == pages[k])
					{
						temp[j] = k;
						break;
					}
				}
			}

			for(j=0; j<nf; j++){
				if(temp[j] == -1)
				{
					pos = j;
					flag3 = 1;
					break;
				}
			}

			if(flag3 == 0)
			{
			max = temp[0];
			pos = 0;

			for(q = 1; q<nf; q++)
			{
				if(max < temp[q])
				{
					max = temp[q];
					pos = q;
				}
			}

			}

			frames[pos] = pages[i];
			faults++;


		}// flag2

		for(k=0;k<nf;k++)
		{
			printf("%d ", frames[k]);
		}

		printf("\n");
	}

	printf("Faults = %d\n", faults);

	printf("\n");
	return 0;
}