页面置换算法LRU算法c代码

以下是LRU算法的C代码实现：

#include <stdio.h>
#include <stdlib.h>

#define CACHE_SIZE 4

typedef struct node {
    int data;
    struct node* next;
} Node;

Node* head = NULL;
int cache[CACHE_SIZE] = {0};
int cache_count = 0;

void print_cache() {
    printf("Cache: ");
    for (int i = 0; i < CACHE_SIZE; i++) {
        printf("%d ", cache[i]);
    }
    printf("\n");
}

void add_to_cache(int page) {
    if (cache_count < CACHE_SIZE) {
        cache[cache_count++] = page;
    } else {
        Node* current = head;
        while (current->next != NULL) {
            current = current->next;
        }
        int oldest_page = current->data;
        current->data = page;
        for (int i = 0; i < CACHE_SIZE; i++) {
            if (cache[i] == oldest_page) {
                cache[i] = page;
                break;
            }
        }
    }
}

void access_page(int page) {
    for (int i = 0; i < CACHE_SIZE; i++) {
        if (cache[i] == page) {
            printf("Page %d is already in cache.\n", page);
            return;
        }
    }
    printf("Page %d is not in cache.\n", page);
    add_to_cache(page);
    print_cache();
}

int main() {
    head = (Node*)malloc(sizeof(Node));
    head->data = -1;
    head->next = NULL;

    access_page(1);
    access_page(2);
    access_page(3);
    access_page(4);
    access_page(1);
    access_page(2);
    access_page(5);
    access_page(1);
    access_page(2);
    access_page(3);
    access_page(4);
    access_page(5);

    return 0;
}

这段代码实现了LRU算法的缓存置换策略。当访问一个页面时，如果该页面已经在缓存中，则直接返回；否则，将该页面加入缓存中，并将最久未被访问的页面替换掉。