写入输出文件的 C++ 星形菱形图案变得混乱

Question

我正在学习用 C++ 编写代码并进行简单的初学者练习。目前，我遇到一个问题，即我的星形菱形图案输出正确到控制台，但 相同的文件输出变得混乱。

此程序根据行长创建 a * star diamond，并尝试将相同的设计保存到名为 output_diamond.txt.[=14= 的输出文件中]

关于如何处理此类问题的任何提示或解决方案？我知道 C++ 部分非常严格，我确保记录我的代码并提供一个可重新创建的工作示例。

代码

#include <iostream>
#include <string>
#include <fstream>
#include <cassert>

using namespace std;

void pyramid(int rows);
int main() {
    pyramid(8);
    return 0;
}

/*
 * @param int rows
 *
 * Function to output to console a star pyramid
 * based on an amount of rows for a half going
 * vertical. If top half of rows is 8, than the
 * bottom half will be indetical but reverse with
 * a row count of 8.
 */
void pyramid(int rows) {
    ofstream fout;

    fout.open("output_diamond.txt");
    if (fout.is_open()) {
        /* Top Half */
        // Initialize variable for spaces equal to (rows - 1)
        int space = rows - 1;
        // Begin first for loop for top half of diamond
        for (int i = 1; i <= rows; i++) { // For 1
            // Begin for loop for spaces
            for (int count = 1; count <= space; count++) { // For 2
                // Output to console a single space
                cout << ' ';
                fout << " ";
            } // End For 2
            // Begin for loop for star/diamond char symbol
            for (int count = 1; count <= (2 * i) - 1; count++) { // For 3
                // Output to console a single *
                cout << '*';
                fout << '*' << endl;
            } // End For 3
            // Before for loop ends output end of line
            cout << endl;
            // Decrement -1 to space
            space--;
        } // End For 1

        /*  Bottom Half */
        // Set value for space variable to 1
        space = 1;
        // Begin first for loop for bottom half of diamond
        for (int i = 1; i <= rows - 1; i++) { // For 1
            // Begin loop for spaces
            for (int count = 1; count <= space; count++) { // For 2
                // Output to console a single space
                cout << ' ';
                fout << ' ';
            } // End For 2
            // Begin for loop for star/diamond char symbol
            for (int count = 1; count <= (2 * (rows - i)) - 1; count++) { // For 3
                // Output to console a single *
                cout << '*';
                fout << '*' << endl;
            } // End For 3
            // Before for loop ends output end of line
            cout << endl;
            // Increment space +1
            space++;
        } // End For 1
    } else {
        cout << "Output file did not open!" << endl;
        assert(fout);
    }
    // End
}

控制台输出

       *
      ***
     *****
    *******
   *********
  ***********
 *************
***************
 *************
  ***********
   *********
    *******
     *****
      ***
       *

示例文本文件输出

       *
      *
*
*
     *
*
*
*
*
    *
*
*
*
*
*
*
   *
*
*
*
*
*
*
*

Answer 1

您的 cout 和 fout 行应始终成对出现并且应始终相同。

// Output to console a single *
cout << '*';
fout << '*' << endl;

去掉 << endl。这发生在两个地方。

// Before for loop ends output end of line
cout << endl;

添加fout << endl;。这也发生了两次。

Answer 2

实用的解决方案是采用可行的方法并将其推广。有效的是 std::cout 生成的输出，因此所需要的只是编写一个函数，它接受一个流并完全执行 std::cout 正在做的事情。

做到这一点的方法是认识到 std::ostream 是输出流的基础 class，因此所需要的只是使用多态性并编写一个函数来引用std::ostream.

这是一个例子：

#include <iostream>
#include <string>
#include <ostream>
#include <fstream>
#include <sstream>
#include <cassert>

using namespace std;

void pyramid(int rows, std::ostream& );

int main() 
{
    // use regular cout
    std::cout << "Using cout \n\n";
    pyramid(8, std::cout);

    // try file printing
    std::ofstream fout;
    fout.open("output_diamond.txt");
    pyramid(8, fout);

    // try printing to a string stream
    std::cout << "\n\nUsing ostringstream \n\n";
    std::ostringstream ostrm;
    pyramid(8, ostrm);
    std::cout << "\n";
    std::cout << ostrm.str();
    return 0;
}

void pyramid(int rows, std::ostream& sout) 
{
    int space = rows - 1;
    for (int i = 1; i <= rows; i++) { 
        for (int count = 1; count <= space; count++) { 
            sout << ' ';
        } 
        for (int count = 1; count <= (2 * i) - 1; count++) { 
            sout << '*';
        } 
        sout << endl;
        space--;
    } 
    space = 1;
    for (int i = 1; i <= rows - 1; i++) { 
        for (int count = 1; count <= space; count++) { 
            sout << ' ';
        } 
        for (int count = 1; count <= (2 * (rows - i)) - 1; count++) { 
            sout << '*';
        } 
        sout << endl;
        space++;
    }
}

Live Example showing std::cout and std::ostringstream

这是文件的输出：

       *
      ***
     *****
    *******
   *********
  ***********
 *************
***************
 *************
  ***********
   *********
    *******
     *****
      ***
       *

写入输出文件的 C++ 星形菱形图案变得混乱

C++ Star diamond pattern written to output file becomes jumbled

c++

formatting

fstream

iostream