用c语言实现页面置换算法的先进先出（FIFO）算法，最近最久未使用（LRU）算法，时钟（Clock）算法，最不经常使用（LFU）算法，最优（OPT）算法

以下是使用 C 语言实现不同页面置换算法的示例代码：

1. 先进先出（FIFO）算法

#include <stdio.h>

int main() {
    int n, frames, hits = 0, faults = 0, index = 0, flag = 0;
    printf("Enter the number of pages: ");
    scanf("%d", &n);
    int reference_string[n];
    printf("Enter the reference string: ");
    for(int i = 0; i < n; i++) {
        scanf("%d", &reference_string[i]);
    }
    printf("Enter the number of frames: ");
    scanf("%d", &frames);
    int frame[frames];
    for(int i = 0; i < frames; i++) {
        frame[i] = -1;
    }
    for(int i = 0; i < n; i++) {
        flag = 0;
        for(int j = 0; j < frames; j++) {
            if(frame[j] == reference_string[i]) {
                hits++;
                flag = 1;
                break;
            }
        }
        if(flag == 0) {
            frame[index] = reference_string[i];
            faults++;
            index++;
            if(index == frames) {
                index = 0;
            }
        }
        printf("Reference string: ");
        for(int j = 0; j <= i; j++) {
            printf("%d ", reference_string[j]);
        }
        printf("\n");
        printf("Frames: ");
        for(int j = 0; j < frames; j++) {
            printf("%d ", frame[j]);
        }
        printf("\n");
    }
    printf("Page faults: %d\n", faults);
    printf("Page hits: %d\n", hits);
    printf("Hit ratio: %f\n", (float)hits/n);
    return 0;
}

2. 最近最久未使用（LRU）算法

#include <stdio.h>

int main() {
    int n, frames, hits = 0, faults = 0, min, index, flag;
    printf("Enter the number of pages: ");
    scanf("%d", &n);
    int reference_string[n];
    printf("Enter the reference string: ");
    for(int i = 0; i < n; i++) {
        scanf("%d", &reference_string[i]);
    }
    printf("Enter the number of frames: ");
    scanf("%d", &frames);
    int frame[frames];
    int counter[frames];
    for(int i = 0; i < frames; i++) {
        frame[i] = -1;
        counter[i] = 0;
    }
    for(int i = 0; i < n; i++) {
        flag = 0;
        for(int j = 0; j < frames; j++) {
            if(frame[j] == reference_string[i]) {
                hits++;
                flag = 1;
                counter[j] = i;
                break;
            }
        }
        if(flag == 0) {
            faults++;
            min = counter[0];
            index = 0;
            for(int j = 1; j < frames; j++) {
                if(counter[j] < min) {
                    min = counter[j];
                    index = j;
                }
            }
            frame[index] = reference_string[i];
            counter[index] = i;
        }
        printf("Reference string: ");
        for(int j = 0; j <= i; j++) {
            printf("%d ", reference_string[j]);
        }
        printf("\n");
        printf("Frames: ");
        for(int j = 0; j < frames; j++) {
            printf("%d ", frame[j]);
        }
        printf("\n");
    }
    printf("Page faults: %d\n", faults);
    printf("Page hits: %d\n", hits);
    printf("Hit ratio: %f\n", (float)hits/n);
    return 0;
}

3. 时钟（Clock）算法

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

typedef struct {
    int page;
    int use_bit;
} Frame;

int main() {
    int n, frames, hits = 0, faults = 0, flag;
    printf("Enter the number of pages: ");
    scanf("%d", &n);
    int reference_string[n];
    printf("Enter the reference string: ");
    for(int i = 0; i < n; i++) {
        scanf("%d", &reference_string[i]);
    }
    printf("Enter the number of frames: ");
    scanf("%d", &frames);
    Frame frame[frames];
    for(int i = 0; i < frames; i++) {
        frame[i].page = -1;
        frame[i].use_bit = 0;
    }
    int pointer = 0;
    for(int i = 0; i < n; i++) {
        flag = 0;
        for(int j = 0; j < frames; j++) {
            if(frame[j].page == reference_string[i]) {
                hits++;
                frame[j].use_bit = 1;
                flag = 1;
                break;
            }
        }
        if(flag == 0) {
            faults++;
            while(frame[pointer].use_bit == 1) {
                frame[pointer].use_bit = 0;
                pointer = (pointer + 1) % frames;
            }
            frame[pointer].page = reference_string[i];
            frame[pointer].use_bit = 1;
            pointer = (pointer + 1) % frames;
        }
        printf("Reference string: ");
        for(int j = 0; j <= i; j++) {
            printf("%d ", reference_string[j]);
        }
        printf("\n");
        printf("Frames: ");
        for(int j = 0; j < frames; j++) {
            printf("%d ", frame[j].page);
        }
        printf("\n");
    }
    printf("Page faults: %d\n", faults);
    printf("Page hits: %d\n", hits);
    printf("Hit ratio: %f\n", (float)hits/n);
    return 0;
}

4. 最不经常使用（LFU）算法

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

typedef struct {
    int page;
    int freq;
} Frame;

int main() {
    int n, frames, hits = 0, faults = 0, flag, min, index;
    printf("Enter the number of pages: ");
    scanf("%d", &n);
    int reference_string[n];
    printf("Enter the reference string: ");
    for(int i = 0; i < n; i++) {
        scanf("%d", &reference_string[i]);
    }
    printf("Enter the number of frames: ");
    scanf("%d", &frames);
    Frame frame[frames];
    for(int i = 0; i < frames; i++) {
        frame[i].page = -1;
        frame[i].freq = 0;
    }
    for(int i = 0; i < n; i++) {
        flag = 0;
        for(int j = 0; j < frames; j++) {
            if(frame[j].page == reference_string[i]) {
                hits++;
                flag = 1;
                frame[j].freq++;
                break;
            }
        }
        if(flag == 0) {
            faults++;
            min = frame[0].freq;
            index = 0;
            for(int j = 1; j < frames; j++) {
                if(frame[j].freq < min) {
                    min = frame[j].freq;
                    index = j;
                }
            }
            frame[index].page = reference_string[i];
            frame[index].freq = 1;
        }
        printf("Reference string: ");
        for(int j = 0; j <= i; j++) {
            printf("%d ", reference_string[j]);
        }
        printf("\n");
        printf("Frames: ");
        for(int j = 0; j < frames; j++) {
            printf("%d(%d) ", frame[j].page, frame[j].freq);
        }
        printf("\n");
    }
    printf("Page faults: %d\n", faults);
    printf("Page hits: %d\n", hits);
    printf("Hit ratio: %f\n", (float)hits/n);
    return 0;
}

5. 最优（OPT）算法

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

int main() {
    int n, frames, hits = 0, faults = 0, max, index, flag;
    printf("Enter the number of pages: ");
    scanf("%d", &n);
    int reference_string[n];
    printf("Enter the reference string: ");
    for(int i = 0; i < n; i++) {
        scanf("%d", &reference_string[i]);
    }
    printf("Enter the number of frames: ");
    scanf("%d", &frames);
    int frame[frames];
    for(int i = 0; i < frames; i++) {
        frame[i] = -1;
    }
    int next[n];
    for(int i = 0; i < n; i++) {
        next[i] = -1;
        for(int j = i + 1; j < n; j++) {
            if(reference_string[j] == reference_string[i]) {
                next[i] = j;
                break;
            }
        }
    }
    for(int i = 0; i < n; i++) {
        flag = 0;
        for(int j = 0; j < frames; j++) {
            if(frame[j] == reference_string[i]) {
                hits++;
                flag = 1;
                break;
            }
        }
        if(flag == 0) {
            faults++;
            max = -1;
            index = -1;
            for(int j = 0; j < frames; j++) {
                if(next[frame[j]] == -1) {
                    index = j;
                    break;
                }
                if(next[frame[j]] > max) {
                    max = next[frame[j]];
                    index = j;
                }
            }
            frame[index] = reference_string[i];
        }
        printf("Reference string: ");
        for(int j = 0; j <= i; j++) {
            printf("%d ", reference_string[j]);
        }
        printf("\n");
        printf("Frames: ");
        for(int j = 0; j < frames; j++) {
            printf("%d ", frame[j]);
        }
        printf("\n");
    }
    printf("Page faults: %d\n", faults);
    printf("Page hits: %d\n", hits);
    printf("Hit ratio: %f\n", (float)hits/n);
    return 0;
}

以上是使用 C 语言实现不同页面置换算法的示例代码，每个算法的实现方式略有不同，但都是基于相同的基本思想。