分配内存空间，输入两个数组，排序再组合排序

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

int *read_arr1(int);
int *read_arr2(int);
int *order(int *,int);
int *combine(int *,int *,int,int);

int main()
{
    int num_arr1,num_arr2,*ptr_arr1,*ptr_arr2,*com_arr,i;

    printf("Please input the size of arr1：");
    scanf("%d",&num_arr1);
    getchar();
    printf("Please input the size of arr2：");
    scanf("%d",&num_arr2);
    getchar();

    printf("\n\n");

    ptr_arr1=read_arr1(num_arr1);
    ptr_arr2=read_arr2(num_arr2);

    ptr_arr1=order(ptr_arr1,num_arr1);
    ptr_arr2=order(ptr_arr2,num_arr2);

    printf("\n\n");

    printf("The ascending order of arr1 is：");
    for(i=0;i<num_arr1;i++)
    {
        printf("%d  ",ptr_arr1[i]);
    }
    printf("\n");

    printf("The ascending order of arr2 is：");
    for(i=0;i<num_arr2;i++)
    {
        printf("%d  ",ptr_arr2[i]);
    }
    printf("\n");

    com_arr=combine(ptr_arr1,ptr_arr2,num_arr1,num_arr2);
    com_arr=order(com_arr,num_arr1+num_arr2);

    printf("The ascending order of combine of arr1 and arr2 is：");
    for(i=0;i<num_arr1+num_arr2;i++)
    {
        printf("%d  ",com_arr[i]);
    }
    printf("\n");

    return 0;
}

int *read_arr1(int num_arr1)
{
    int *ptr_arr1,i;
    ptr_arr1=malloc(num_arr1*sizeof(int));

    printf("Please iput the elements of arr1：");
    for(i=0;i<num_arr1;i++)
    {
        scanf("%d",&ptr_arr1[i]);
    }
    getchar();
    return ptr_arr1;
}

int *read_arr2(int num_arr2)
{
    int *ptr_arr2,i;
    ptr_arr2=malloc(num_arr2*sizeof(int));

    printf("Please iput the elements of arr2：");
    for(i=0;i<num_arr2;i++)
    {
        scanf("%d",&ptr_arr2[i]);
    }
    getchar();
    return ptr_arr2;
}

int *order(int *arr,int num)
{
    int i,j,temp;
    for(j=0;j<=num-2;j++)
    {
        for (i=0;i<num-j-1;i++)
        {
            if (arr[i]>arr[i+1])
            {
                temp=arr[i];
                arr[i]=arr[i+1];
                arr[i+1]=temp;
            }
        }
    }

    return arr;
}

int *combine(int *ptr_arr1,int *ptr_arr2,int num_arr1,int num_arr2)
{
    int i,j,*com_arr;
    com_arr=malloc(sizeof(int)*(num_arr1+num_arr2));

    for(i=0;i<num_arr1;i++)
    {
        com_arr[i]=ptr_arr1[i];
    }
    for(j=0;j<num_arr2;i++,j++)
    {
        com_arr[i]=ptr_arr2[j];
    }

    return com_arr;
}