C++ 传递指针给函数

#include <iostream>

using namespace std;
double getavg(int *pt,int size);

int main()
    {
     int mat[3]={1000,10,677};

     double avg;

     avg=getavg(mat,3);

     cout<<"the average of mat is "<<avg<<endl;
    }



double getavg(int *pt,int size)
     {
        double sum;
        double avg;

        for (int i=0;i<size;i++)
        {

                sum=sum+pt[i];
        }
        avg=sum/size;
        return avg;

     }
        

the average of mat is 562.333