LRU页面置换算法

本文以序列长度20的{ 7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1};以及页面4；为例；

#include <stdio.h>

#define InitPysiBlocks 4
#define MaxPages 20
int PysicalBlocks[InitPysiBlocks] = { -1,-1,-1,-1 };
int PageSequence[MaxPages] = { 7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1};

void LRU(int py[],int pg[])
{
    int i,j,k,m,flag[MaxPages],temp[MaxPages][InitPysiBlocks];
    int max = 0;
    char f[MaxPages];
    for(i = 0; i < InitPysiBlocks; i++)
    {
        py[i] = pg[i];
        flag[i] = i;
        f[i] = '*';
        for(j = 0; j < InitPysiBlocks; j++)
            temp[i][j] = py[j];
    }
    for(i = InitPysiBlocks; i < MaxPages; i++)
    {
        for(j = 0,k = 0; j < InitPysiBlocks; j++)
        {
            if(py[j] != pg[i])
                k++;
            else
                flag[j] = i;
        }
        if(k == InitPysiBlocks)
        {
            f[i] = '*';
            max = flag[0] < flag[1]?0:1;
            for(m = 2; m < InitPysiBlocks; m++)
                if(flag[m] < flag[max])
                    max = m;
            py[max] = pg[i];
            flag[max] = i;
            for(j = 0; j < InitPysiBlocks; j++)
                temp[i][j] = py[j];
        }
        else
        {
            f[i] = ' ';
            for(j = 0; j < InitPysiBlocks; j++)
                temp[i][j] = py[j];
        }
    }
    printf("输出结果为下表(-1代表为空,*代表有缺页)：
");
    for(i = 0; i < InitPysiBlocks; i++)
    {
        for(j = 0; j < MaxPages; j++)
            printf("%3d",temp[j][i]);
        printf("
");
    }
    for(i = 0; i < MaxPages; i++)
        printf("%3c",f[i]);
    printf("
");
}

void main()
{
    LRU(PysicalBlocks,PageSequence);
}

测试：