class A {
public:
  void getVal() {
    ptr = arr1;
    ptr = arr2;
    Serial.println(sizeof(ptr));
  }
private:
  int* ptr;
  int arr1[4] = {0,1,2,3};
  int arr2[3] = {55,66,77};
};

A a;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  a.getVal();
//  Serial.println(a.getVal());
}

void loop() {
  // put your main code here, to run repeatedly:

}