如何在屏幕上显示输出

How to show output on screen?

本文关键字：显示 输出 屏幕      更新时间：2023-10-16

我正在练习Alex Allain书中的数组和指针。

#include <iostream>
#include <fstream>
using namespace std;
int *growArray (int* p_values, int cur_size);
int main ()
{
  int next_element = 0;
  int size = 10;
  int *p_values = new int[ size ];
  int val;
  cout << "Please enter a number: ";
  cin >> val;
  while ( val > 0 )
  {
    if ( size == next_element + 1 )
    {
      // now all we need to do is implement growArray
      p_values = growArray( p_values, size );
    }
    p_values[ next_element ] = val;
    cout << "Please enter a number (or 0 to exit): ";
    cin >> val;
  }
}
int *growArray (int* p_values, int cur_size)
{
  int *p_new_values = new int[ cur_size * 2 ];
  for ( int i = 0; i < cur_size; ++i )
  {
    p_new_values[ i ] = p_values[ i ];
    cout << p_new_values[ i ] << endl;
  }
  delete p_values;
  return p_new_values;
}
但是当我执行代码 时
Please enter a number: 6
Please enter a number (or 0 to exit): 0

为什么我缺少p_new_values阵列的屏幕输出?是否允许将cout放入函数定义中?

if ( size == next_element + 1 )
{
    // now all we need to do is implement growArray
    p_values = growArray( p_values, size );
}

size永远不会是next_element + 1，所以你的growArray函数永远不会被调用。

请注意，当next_element仅比当前数组大1时，size将等于next_element + 1，因此当next_element是size-1时，growArray()函数将在程序的特定点调用，等等。

if ( size == next_element + 1 )
{
    // now all we need to do is implement growArray
    p_values = growArray( p_values, size );
}

同样，变量next_element没有得到更新以使条件成为有效的逻辑。

您可以替换以下行:

p_values[ next_element ] = val;


p_values[ next_element++ ] = val;
最终代码:

#include <iostream>
#include <fstream>
using namespace std;
int *growArray (int* p_values, int *cur_size);   //Changed
int main ()
{
  int next_element = 0;
  int size = 10;
  int *p_values = new int[ size ];
  int val;
  cout << "Please enter a number: ";
  cin >> val;
  while ( val > 0 )
  {
    if ( size == next_element + 1 )
    {
      // now all we need to do is implement growArray
      p_values = growArray( p_values, &size );    //Changed
    }
    p_values[ next_element++ ] = val;    //Changed
    cout << "Please enter a number (or 0 to exit): ";
    cin >> val;
  }
}
int *growArray (int* p_values, int *cur_size)    //Changed
{
  *cur_size = *cur_size * 2;                     //Changed
  int *p_new_values = new int[ *cur_size];       //Changed
  for ( int i = 0; i < *cur_size; ++i )          //Changed
  {
    p_new_values[ i ] = p_values[ i ];
    cout << p_new_values[ i ] << endl;
  }
  delete p_values;
  return p_new_values;
}

仅在出现使用*growArray()函数的情况下才尝试打印值，因为打印语句在*growArray()函数内部。

在函数定义中使用cout是完全可以的。

[edit]和是的，如上所述，您没有更改参数next_element，因此应该重新检查您的逻辑。

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