C语言 定义一个含有20个元素的double型数组a，定义一个指针变量ptrDouble指向该数组

#include int main(){ double a[20]; double* ptrDouble = a; double sum = 0; int i = 0; for (i = 0; i < 20; i++) *(ptrDouble + i) = 3.2 * i + 1.5; ptrDouble = a + 10; for (i = 0; i < 10; i++) sum += *(ptrDouble + i); for (i = -10; i < 10; i++) pr