c语言把两个已按升序排列的数组合并成一个升序数组，要求用函数实现。

好的，下面是代码实现：

#include <stdio.h>

void merge(int arr1[], int arr2[], int len1, int len2, int merged[]) {
    int i = 0, j = 0, k = 0;

    while (i < len1 && j < len2) {
        if (arr1[i] < arr2[j]) {
            merged[k++] = arr1[i++];
        } else {
            merged[k++] = arr2[j++];
        }
    }

    while (i < len1) {
        merged[k++] = arr1[i++];
    }

    while (j < len2) {
        merged[k++] = arr2[j++];
    }
}

int main() {
    int arr1[] = {1, 3, 5, 7, 9};
    int arr2[] = {2, 4, 6, 8, 10};
    int len1 = sizeof(arr1) / sizeof(arr1[0]);
    int len2 = sizeof(arr2) / sizeof(arr2[0]);
    int merged[len1 + len2];
    int i;

    merge(arr1, arr2, len1, len2, merged);

    printf("合并后的升序数组为：");
    for (i = 0; i < len1 + len2; i++) {
        printf("%d ", merged[i]);
    }
    printf("\n");

    return 0;
}

定义了一个函数 `merge`，用于将两个已按升序排列的数组 `arr1` 和 `arr2`