c语言编写两个函数，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。

以下是实现这个需求的代码：

1. 求次大值和次小值的函数 - second_largest_smallest.c

#include <stdio.h>

void second_largest_smallest(int arr[], int n, int *second_largest, int *second_smallest) {
    int largest = arr[0], smallest = arr[0];

    for (int i = 1; i < n; i++) {
        if (arr[i] > largest) {
            *second_largest = largest;
            largest = arr[i];
        } else if (arr[i] > *second_largest && arr[i] != largest) {
            *second_largest = arr[i];
        }

        if (arr[i] < smallest) {
            *second_smallest = smallest;
            smallest = arr[i];
        } else if (arr[i] < *second_smallest && arr[i] != smallest) {
            *second_smallest = arr[i];
        }
    }
}

2. 求最大公约数和最小公倍数的函数 - gcd_lcm.c

#include <stdio.h>

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

int lcm(int a, int b) {
    return (a * b) / gcd(a, b);
}

3. 主函数 - main.c

#include <stdio.h>
#include "second_largest_smallest.h"
#include "gcd_lcm.h"

int main() {
    int arr[10];
    printf("Enter 10 integers: ");
    for (int i = 0; i < 10; i++) {
        scanf("%d", &arr[i]);
    }

    int second_largest = arr[0], second_smallest = arr[0];
    second_largest_smallest(arr, 10, &second_largest, &second_smallest);

    printf("Second largest number is %d\n", second_largest);
    printf("Second smallest number is %d\n", second_smallest);
    printf("GCD of %d and %d is %d\n", second_largest, second_smallest, gcd(second_largest, second_smallest));
    printf("LCM of %d and %d is %d\n", second_largest, second_smallest, lcm(second_largest, second_smallest));

    return 0;
}

4. 头文件 - second_largest_smallest.h 和 gcd_lcm.h

#ifndef SECOND_LARGEST_SMALLEST_H
#define SECOND_LARGEST_SMALLEST_H

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

#endif

#ifndef GCD_LCM_H
#define GCD_LCM_H

int gcd(int a, int b);
int lcm(int a, int b);

#endif

注意：以上代码需要分别存储为4个文件，并放在同一个目录下进行编译和链接。