c语言代码编写两个函数，其功能分别为: ①求N个整数的次大值和次小值。 ②求两个整数的最大公约数和最小公倍数。 输人10个整数，调用函数求它们的次大值和次小值，及次大值和次小值的最大公约数和最小公倍数。 要求:这两个函数和主函数分属3个文件。

以下是代码实现，分别保存为三个文件：

1. main.c

#include <stdio.h>
#include "second_largest_and_smallest.h"
#include "gcd_and_lcm.h"

#define N 10

int main() {
    int arr[N];
    printf("Please enter %d integers:\n", N);
    for (int i = 0; i < N; i++) {
        scanf("%d", &arr[i]);
    }
    int second_largest, second_smallest;
    find_second_largest_and_smallest(arr, N, &second_largest, &second_smallest);
    printf("Second largest: %d\nSecond smallest: %d\n", second_largest, second_smallest);

    int a, b;
    printf("Please enter two integers:\n");
    scanf("%d%d", &a, &b);
    int gcd = find_gcd(a, b);
    int lcm = find_lcm(a, b);
    printf("GCD: %d\nLCM: %d\n", gcd, lcm);
    return 0;
}

2. second_largest_and_smallest.h

#ifndef SECOND_LARGEST_AND_SMALLEST_H
#define SECOND_LARGEST_AND_SMALLEST_H

void find_second_largest_and_smallest(int arr[], int n, int *second_largest, int *second_smallest);

#endif //SECOND_LARGEST_AND_SMALLEST_H

3. second_largest_and_smallest.c

#include "second_largest_and_smallest.h"

void find_second_largest_and_smallest(int arr[], int n, int *second_largest, int *second_smallest) {
    // Initialize the largest and smallest variables to be the first element in the array
    int largest = arr[0], smallest = arr[0];
    // Initialize the second largest and smallest variables to be the same as largest and smallest
    *second_largest = largest;
    *second_smallest = smallest;

    for (int i = 1; i < n; i++) {
        if (arr[i] > largest) {
            // If the current element is larger than the largest, update the second largest and largest
            *second_largest = largest;
            largest = arr[i];
        } else if (arr[i] > *second_largest) {
            // If the current element is between the largest and second largest, update the second largest
            *second_largest = arr[i];
        }

        if (arr[i] < smallest) {
            // If the current element is smaller than the smallest, update the second smallest and smallest
            *second_smallest = smallest;
            smallest = arr[i];
        } else if (arr[i] < *second_smallest) {
            // If the current element is between the smallest and second smallest, update the second smallest
            *second_smallest = arr[i];
        }
    }
}

4. gcd_and_lcm.h

#ifndef GCD_AND_LCM_H
#define GCD_AND_LCM_H

int find_gcd(int a, int b);

int find_lcm(int a, int b);

#endif //GCD_AND_LCM_H

5. gcd_and_lcm.c

#include "gcd_and_lcm.h"

int find_gcd(int a, int b) {
    if (b == 0) {
        return a;
    }
    return find_gcd(b, a % b);
}

int find_lcm(int a, int b) {
    int gcd = find_gcd(a, b);
    return a * b / gcd;
}