将 1 个 C++ 循环变为 2 个答案

【问题标题】：Turn 1 C++ Loop into 2将 1 个 C++ 循环变为 2 个
【发布时间】：2010-12-06 03:58:02
【问题描述】：

我需要一点编程帮助来上课。我写了下面的代码，但是我的老师说我在读取数据文件时需要使用 2 个 for 循环。我不知道该怎么做...有什么建议吗？

我的代码：

ifstream infile;
infile.open("dive.txt");
for(int i = 0; i <= 6; i++)
    infile >> contestantNames[i][0] >> contestantNames[i][1] >> judgeScores[i][0] >> judgeScores[i][1] >> judgeScores[i][2] >> judgeScores[i][3] >> judgeScores[i][4] >> judgeScores[i][5] >> judgeScores[i][6] >> judgeScores[i][7];
infile.close();

【问题讨论】：

您的老师可能希望您使用两个嵌套循环，而不是手动从 0 变为 7。
能否请您为 100 位参赛者发布您的示例？（与contestantNames[100][100]）

标签： c++ loops for-loop

【解决方案1】：

不要重复写

infile >> contestantNames[0][0] >> contestantNames[0][1] >> judgeScores[0][0] >> judgeScores[0][1] >> judgeScores[0][2] >> judgeScores[0][3] >> judgeScores[0][4] >> judgeScores[0][5] >> judgeScores[0][6] >> judgeScores[0][7];
infile >> contestantNames[1][0] >> contestantNames[1][1] >> judgeScores[1][0] >> judgeScores[1][1] >> judgeScores[1][2] >> judgeScores[1][3] >> judgeScores[1][4] >> judgeScores[1][5] >> judgeScores[1][6] >> judgeScores[1][7];
infile >> contestantNames[2][0] >> contestantNames[2][1] >> judgeScores[2][0] >> judgeScores[2][1] >> judgeScores[2][2] >> judgeScores[2][3] >> judgeScores[2][4] >> judgeScores[2][5] >> judgeScores[2][6] >> judgeScores[2][7];
infile >> contestantNames[3][0] >> contestantNames[3][1] >> judgeScores[3][0] >> judgeScores[3][1] >> judgeScores[3][2] >> judgeScores[3][3] >> judgeScores[3][4] >> judgeScores[3][5] >> judgeScores[3][6] >> judgeScores[3][7];
infile >> contestantNames[4][0] >> contestantNames[4][1] >> judgeScores[4][0] >> judgeScores[4][1] >> judgeScores[4][2] >> judgeScores[4][3] >> judgeScores[4][4] >> judgeScores[4][5] >> judgeScores[4][6] >> judgeScores[4][7];
infile >> contestantNames[5][0] >> contestantNames[5][1] >> judgeScores[5][0] >> judgeScores[5][1] >> judgeScores[5][2] >> judgeScores[5][3] >> judgeScores[5][4] >> judgeScores[5][5] >> judgeScores[5][6] >> judgeScores[5][7];
infile >> contestantNames[6][0] >> contestantNames[6][1] >> judgeScores[6][0] >> judgeScores[6][1] >> judgeScores[6][2] >> judgeScores[6][3] >> judgeScores[6][4] >> judgeScores[6][5] >> judgeScores[6][6] >> judgeScores[6][7];

你写了一个for循环。

哪里还有重复？

【讨论】：

【解决方案2】：

你的两个 for 循环是

for (int i = 0; i <= 6; i++) {
    infile >> contestantNames[i][0] >> contestantNames[i][1];
    for (int j = 0; j <= 7; j++) {
        infile >> judgeScores[i][j];
    }
}

您的教师希望您将连续的judgeScores 简化为一个更简单、更易于阅读的for 循环。

【讨论】：

【解决方案3】：

ifstream infile;
infile.open("dive.txt");

for (int i = 0; i <= 6; i++)
{
  infile >> contestantNames[i][0] >> contestantNames[i][1];

  // The next part is what your teacher was talking about.
  // You wrote judgeScores[i][0] >> judgeScores[i][1] >> ...
  // seven times, which is pretty redundant. Programmers are *extremely* lazy
  // so we loop constantly, wherever possible:

  for (int j = 0; j <= 7; j++)
  {
     infile >> judgeScores[i][j];
  }
}

infile.close();

【讨论】：

【解决方案4】：

如果有两个以上的参赛者，您的老师可能希望您考虑这种情况。类似于

nc = 6;  // the number of contenstans
for (int c=0; c<nc; c++) {
  // other for loop here...
}

【讨论】：

【解决方案5】：

我认为您的教练的意思是循环遍历所有参赛者，然后再次循环输入每个参赛者的信息（姓名和分数）。

所以试试这样的：

ifstream infile;
infile.open("dive.txt");
for(int i = 0; i <= 6; i++) {
    infile >> contestantNames[i][0] >> contestantNames[i][1];
    for (int j = 0; i <= 7; j++) {
         infile >> judgeScores[i][j];
    }
}
infile.close();

注意：括号不是必需的，因为每个语句由一行组成。这是规则的例外，但是 - 如果for 循环中有超过 1 个语句，则需要括号。（你可能知道。）

【讨论】：

【解决方案6】：

连三个循环都让你的老师大吃一惊：

ifstream infile;
infile.open("dive.txt");
for(int i = 0; i <= 6; i++)
{
    for (int j = 0; j < 2; ++j)
    {
        infile >> contestantNames[i][j];
    }

    for (int j = 0; j < 8; ++j)
    {
       infile >> judgeScores[i][j];
    }
}
infile.close();

【讨论】：

任何以“让你的老师大吃一惊”开头的建议都应该立即发出警告。
@Cody Gray：为什么不呢？我的意思是好的。如您所见，此版本是这里唯一的版本，可以更轻松地更改contestants 的数量。如果我是老师，我很想看到这个版本。

【解决方案7】：

如果超过 6 行，请使用 while 循环检查文件结尾 (EOF)。不良数据的测试用例也不会受到伤害。

【讨论】：