请教一下，怎么将如下的编码改成图片中的要求？对于这节的知识点有点迷糊。
// declare functions
// note there are two functions declared
float sum1(float array[], int num_elements);
float sum2(float *a, int num_elements);

// define function
float sum1(float array[], int num_elements)
{
 float arraysum = 0.;
 int i;
 for (i=0; i<num_elements; i++)
{
 arraysum = arraysum + array[i];
}
// a test, change last element array[num_elements-1] = 0.;

 return arraysum;
}

//define function
float sum2(float *a, int num_elements)

int main()
{
 float input[4];
 float sum;

 printf("enter four floats\n");
 scanf("%f %f %f %f",&input[0],&input[1],&input[2],&input[3]);
 printf("last element is %f\n",input[3]);
 // call function 1
 sum = sum1(input,4);
 printf("array sum = %f\n",sum);
 printf("last element is %f\n",input[3]);
 // call function 2
 sum = sum2(input,4);
 printf("array sum = %f\n",sum);
 return 0;
}