多行标准输入 - C++

Question

因此，如果我有一个采用标准输入的程序，例如

1
5
2
4

我如何准确地遍历每一行并说打印该值，这就是我的想法：

#include <iostream>
using namespace std;

int main()
{

  while ( // input has ended// ) {
  cout << //current line//

  //increment to next line//

 }     

  return 0;
}

有没有这样的方法？

Answer 1

我喜欢的模式是：

while (!cin.eof())
{
    string line;
    getline(cin, line);

    if (cin.fail())
    {
        //error
        break;
    }

    cout << line << endl;
}

与其他答案一样，您可以键入CTRL+Z以发送EOF至STDIN. 如果STDIN是管道，则将EOF在流没有更多数据时发送。

要保存到向量中：

vector<int> numbers;

while (!cin.eof())
{
    string line;
    getline(cin, line);

    if (cin.fail())
    {
        //error
        break;
    }

    cout << line << endl;

    istringstream iss(line);
    int num;
    iss >> num;
    numbers.push_back(num);
}

如果你想要一个 C 风格的数组（虽然我会推荐std::vector：

size_t START_SIZE = 100;

size_t current_size = START_SIZE;
size_t current_index = 0;

int* numbers = new int[current_size];

while (!cin.eof())
{
    string line;
    getline(cin, line);

    if (cin.fail())
    {
        //error
        break;
    }

    cout << line << endl;

    if (current_index == current_size)
    {
        current_size += START_SIZE;
        int* tmp_arr = new int[current_size];

        for (size_t count = 0; count < current_index; count++)
        {
            tmp_arr[count] = numbers[count];
        }

        delete [] numbers;
        numbers = tmp_arr;
    }

    istringstream iss(line);
    int num;
    iss >> num;

    numbers[current_index] = num;
    current_index++;
}

delete [] numbers;