LRU.cpp

#include<bits/stdc++.h>

int present(int table_frame[], int nf, int page)
{
	for(int i=0; i<nf; i++)
		if(page == table_frame[i])
			return 1;
	return 0;
}

void printtable(int table_frame[], int nf,int time[])
{
	for(int i=0; i<nf; i++)
	{
		if(table_frame[i] == -1)
			printf("-- ");
		else
			printf("%2d (%d) ", table_frame[i],time[i]);			
	}
	printf("||");
}

int findpos(int table_frame[], int nf, int pages[], int curr, int np)
{
	for(int i=0; i<nf; i++)
		if(table_frame[i] == -1)
			return i;

	int pos[nf] = {0};
	for(int i=0; i<nf; i++)
	{
		pos[i] = -1e9;
		for(int j=curr-1; j>=0; j--)
			if(pages[j] == table_frame[i])
			{
				pos[i] = j;
				break;
			}
	}

	int min1 = 1000000, retPos = -1;
	for(int i=0; i<nf; i++)
		if(min1 > pos[i])
		{
			min1 = pos[i];
			retPos = i;
		}

	return retPos;
}

int main()
{
    //nf-number of frames
    int n,nf,i,pos=0;
	int time[3];
    time[0] = 1;
    time[1] = 2;
    time[2] = 3;

    printf("enter number of frames\n"); // ÇÁ·¹ÀÓ ¼ö ÀÔ·Â  
    scanf("%d",&nf);
    int table_frame[nf];
    for(i=0;i<nf;i++)
    {
        table_frame[i]=-1; 
    }

    printf("enter total number of page requests\n");
    scanf("%d",&n);
    int pages[n];
    printf("enter pages\n");
    for(i=0;i<n;i++)
    {
        scanf("%d",&pages[i]);
    }

    int count1=0;
    printf("position of frame table after each request\n");
    for(i=0;i<n;i++)
    {
        printf("page table after request from %2d || ",pages[i]);
        if(!present(table_frame,nf,pages[i]))
        {
             int pos = findpos(table_frame,nf,pages,i,n);
             table_frame[pos]=pages[i];
             time[pos] = i;

             printtable(table_frame,nf,time);
             printf("page fault\n");
             count1++;
             continue;
        }
        printtable(table_frame,nf,time);
		printf("\n");

    }
    printf("\nNumber of page faults : %d\n\n", count1);
}