使用 cout 和字符串格式化列

Question

晚上好！我希望我能请你帮忙格式化 cout 语句中的字符串。

目标是让所有列左对齐，最大宽度为 colWidth。

在下面的输出中，您会注意到列宽按预期执行，除非字符串长度低于列宽（与库存项目 3 一样）。如果我将 string(strArray[i].begin(), strArray[i].begin() + colWidth) 替换为 strArray[i]，则会发生完全相反的情况，即 max 列以下的任何字符串元素都可以，但其他任何内容都会溢出并推出文本。

#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <cstdlib>
using namespace std;

int main()
{
    string strArray[20] = {"mumblemumble1","mumblemumblemumble2","mumble3","mumblemumblemumblemumble4","mumblemumblemumble5","mumble6","mumblemumblemumblemumble7","mumblemumblemumble8","mumble9","mumblemumblemumblemumble10","mumblemumble11","mumblemumblemumble12","mumble13","mumblemumblemumblemumble14","mumblemumblemumble15","mumblemumble16","mumblemumblemumble17","mumble18","mumblemumblemumblemumble19","mumblemumblemumble20"};
    int cols = 2;       // The number of columns to display
    int colWidth = 10;  // Width allowed for title output
    int colCount = 0;   // Used with mod (%) to provide a new line when needed

    cout << endl << endl << "Number of titles in inventory: " << 20;
    cout << endl << endl;

    for(int i = 0; i < 20; i++)
    {
        cout << setw(4) << right << (i + 1) << ") " << left << setw(colWidth) << string(strArray[i].begin(),strArray[i].begin() + colWidth);
        if ((i+1) % cols == 0)
            cout << endl;
    }

    return 1;
}

产生以下输出：

Number of titles in inventory: 20

   1) mumblemumb   2) mumblemumb
   3) mumble3   4) mumblemumb
   5) mumblemumb   6) mumble6
   7) mumblemumb   8) mumblemumb
   9) mumble9  10) mumblemumb
  11) mumblemumb  12) mumblemumb
  13) mumble13  14) mumblemumb
  15) mumblemumb  16) mumblemumb
  17) mumblemumb  18) mumble18
  19) mumblemumb  20) mumblemumb

Answer 1

此代码 string(strArray[i].begin(),strArray[i].begin() + colWidth) 在字符串短于 10 个字符时抛出异常（例如 'mumble3'）。

将您的 for 循环更改为：

for (int i = 0; i < 20; i++)
{
    string str = strArray[i];
    while (str.size() < colWidth) {
        str = str + " ";
    }
    cout << setw(4) << right << (i + 1) << ") " << left << setw(colWidth) << string(str.begin(), str.begin() + colWidth);
    if ((i + 1) % cols == 0)
        cout << endl;
}

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