编写一段C程序,在一个请求分页系统中,假如一个作业的页面走向为:1,2,3,4,1,2,5,1,2,3,4,5。当分配给该作业的物块数为3,分别采用先进先出算法(FIFO) 、最佳淘汰算法(OPT)、最近最少使用算法(LRU),

以下是C语言实现请求分页系统中三种算法的代码：

1. 先进先出算法(FIFO)

#include <stdio.h>
#define MAX 3

int main()
{
    int pages[] = {1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5};
    int frames[MAX], faults = 0, pointer = 0, flag1, flag2, i, j, k;

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

    for(i = 0; i < 12; ++i)
    {
        flag1 = flag2 = 0;

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

        if(flag1 == 0)
        {
            frames[pointer] = pages[i];
            ++pointer;
            ++faults;

            if(pointer == MAX)
                pointer = 0;
        }

        printf("\n");

        for(j = 0; j < MAX; ++j)
            printf("%d\t", frames[j]);
    }

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

    return 0;
}

2. 最佳淘汰算法(OPT)

#include <stdio.h>
#define MAX 3

int main()
{
    int pages[] = {1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5};
    int frames[MAX], faults = 0, flag1, flag2, flag3, i, j, k, pos, max;

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

    for(i = 0; i < 12; ++i)
    {
        flag1 = flag2 = 0;

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

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

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

            for(j = 0; j < MAX; ++j)
            {
                pos = 0;

                for(k = i + 1; k < 12; ++k)
                {
                    if(frames[j] == pages[k])
                    {
                        if(k > pos)
                        {
                            pos = k;
                            flag3 = 1;
                        }
                    }
                }

                if(flag3 == 0)
                {
                    pos = j;
                    break;
                }
            }

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

        printf("\n");

        for(j = 0; j < MAX; ++j)
            printf("%d\t", frames[j]);
    }

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

    return 0;
}

3. 最近最少使用算法(LRU)

#include <stdio.h>
#define MAX 3

int main()
{
    int pages[] = {1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5};
    int frames[MAX], faults = 0, flag1, flag2, flag3, i, j, k, pos, max, counter[MAX];

    for(i = 0; i < MAX; ++i)
    {
        frames[i] = -1;
        counter[i] = 0;
    }

    for(i = 0; i < 12; ++i)
    {
        flag1 = flag2 = 0;

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

        if(flag1 == 0)
        {
            for(j = 0; j < MAX; ++j)
            {
                if(counter[j] == 0)
                {
                    pos = j;
                    flag2 = 1;
                    break;
                }
            }

            if(flag2 == 0)
            {
                max = counter[0];
                pos = 0;

                for(j = 1; j < MAX; ++j)
                {
                    if(counter[j] > max)
                    {
                        max = counter[j];
                        pos = j;
                    }
                }
            }

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

            for(j = 0; j < MAX; ++j)
                counter[j]++;

            counter[pos] = 0;
        }

        printf("\n");

        for(j = 0; j < MAX; ++j)
            printf("%d\t", frames[j]);
    }

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

    return 0;
}