从文件c ++读取/写入数组

Question

我是 C++ 的初学者，我试图弄清楚文件中的输入/输出是如何工作的。该程序应该将整数数组写入文件，然后从文件中读取，对其进行排序，获取平方整数的数量，然后将结果写回文件中。但是，当我尝试编译它时，它告诉我认为““

#include <iostream>
#include <fstream>
using namespace std;

void sorting(int *p);
int squares(int *p);
int main() {
   int i, arr[10], *p = &arr[0], sq;
   char name[50];
   cout << "Give the file's name:";
   cin >> name;
   ofstream myfile(name, ios::out);
   cout << "Give the elements:";
   for (i = 0; i < 10; i++)
      myfile << *(p + i);
   myfile.close();

   ifstream myfile(name, ios::in);
   for (i = 0; i < 10; i++)
      myfile >> *(p + i);
   sq = squares(arr);
   sorting(arr);
   myfile.close();
   ofstream myfile(name, ios::app);
   for (i = 0; i < 10; i++) {
      myfile << "The sorted array is:";
      myfile << *(p + i);
   }
   myfile << "The number of square numbers is: " << sq;
   myfile.close();
   return 0;
}
void sorting(int *p) {
   int temp;
   for (int i = 0; i < 9; i++)
      for (int j = i + 1; j < 10; j++)
         if (*(p + i)>*(p + j)) {
            temp = *(p + i);
            *(p + i) = *(p + j);
            *(p + j) = temp;
         }
}
int squares(int *p) {
   int count = 0;
   for (int i = 0; i < 10; i++)
      if ((*(p + i) % 2) == 0)
         count++;

   return count;
}

Answer 1

您多次重新定义myfile。更改 main() 以便每个声明都是唯一的。这编译在GCC

int main() {
   int i, arr[10], *p = &arr[0], sq;
   char name[50];
   cout << "Give the file's name:";
   cin >> name;
   ofstream myfile1(name, ios::out);
   cout << "Give the elements:";
   for (i = 0; i < 10; i++)
      myfile1 << *(p + i);
   myfile1.close();

   ifstream myfile2(name, ios::in);
   for (i = 0; i < 10; i++)
      myfile2 >> *(p + i);
   sq = squares(arr);
   sorting(arr);
   myfile2.close();
   ofstream myfile3(name, ios::app);
   for (i = 0; i < 10; i++) {
      myfile3 << "The sorted array is:";
      myfile3 << *(p + i);
   }
   myfile3 << "The number of square numbers is: " << sq;
   myfile3.close();
   return 0;
}