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我在一本书中找到了以下代码。老实说，我不知道如何解释和评论我在书中找到的东西。

private int GreatestIncrease(List<int> PopulationList)                              //Imports the population list to Greatest.

{
    int amountOfChange = 0;
    int changeInYears = 0;
    int i;
    int theChange = 0;
    int currentYear = 0;

    for (i = 1; i < PopulationList.Count(); i++)
    {
        theChange = PopulationList[i] - PopulationList[i - 1];
        currentYear = i;

        if (theChange > amountOfChange)
        {
            amountOfChange = theChange;
            changeInYears = i;
        }
    }

    return changeInYears;
}

private int LeastIncrease(List<int> PopulationList)                                 //Imports the population list to Least.
{
    int firstItem = PopulationList.First();
    int lastItem = PopulationList.Last();

    int amountOfChange = (lastItem - firstItem);
    int changeInYears = 0;
    int i;
    int theChange = 0;
    int CurrentYear = 0;

    for (i = 1; i < PopulationList.Count(); i++)
    {
        theChange = PopulationList[i] - PopulationList[i - 1];
        CurrentYear = i;

        if (theChange < amountOfChange)
        {
            amountOfChange = theChange;
            changeInYears = i;
        }
    }

    return changeInYears;
}
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3 回答 3

1

代码遍历一个列表，这就是循环的用途。

amountOfChange 存储到列表当前位置的最大变化。

changeInYears 存储列表中发生更改的位置。如果 i 是年份，则 i-1 到 i 之间发生变化。

由于第一年（i=0）没有变化，因此您从第二年（i=1）开始与前一年进行比较（这就是列表从位置 1 开始的原因）。

theChange 和 currentYear 是用于存储当前更改的时间值，然后将其与当前最大值 (changeInYears) 进行比较，并在更改大于当前最大值时更新（位置，changeInYears 也是如此）。这计算为当前值与列表中先前值之间的差异。

第二种方法完全相同，但存储最小值。

希望能帮助到你

于 2013-09-26T17:38:16.040 回答
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代码从第二个开始遍历列表中的项目，然后从前一个项目的值中减去该值。这就是项目之间的“差异”。然后，项目通过跟踪到目前为止计算的最高/最低值并将其与最新计算的差异进行比较来获取该值的最小值/最大值。如果它确定最后计算的差值高于/低于最佳值，它会存储该差值的值和发生差值的索引。

于 2013-09-26T17:34:54.853 回答
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这有帮助吗？（老实说，你的问题是模糊和开放式的......）

以下代码在单击某个按钮时向页面显示一些信息。它显示了人口的平均变化，人口增长最多和最少的年份。

    private void btnFindPopulation_Click(object sender, EventArgs e)
    {

        StreamReader inputFile = File.OpenText("USPopulation.txt");                     //Open the USPopulation.txt file.

        List<int> PopulationList = new List<int>();                                     //Creates a list and a new object of the list.

        int startingyear = 1950;                                                        //Creates the starting year for the index.

        while (!inputFile.EndOfStream)                                                  //While not at the end of the list.
        {
            PopulationList.Add(int.Parse(inputFile.ReadLine()));                        //Read the scores into the list.
        }


        inputFile.Close();                                                              //Close the file.

       int numberOfYears = PopulationList.Count();                                      //Counts the amount of items in the population and assigns it to number of years.

       int average = Average(PopulationList, numberOfYears);                            //Sends the population list and numberofyears into average.

       lblAnnualChange.Text = average.ToString();                                       //Assigns the new average into the lblAnnualChange.

       int biggest = startingyear + GreatestIncrease(PopulationList);                   //Adds the starting year with the index count of the biggest number.

       lblGreatestIncrease.Text = biggest.ToString();                                   //Assigns the biggest into the lblGreatestIncrease.

       int least = startingyear + LeastIncrease(PopulationList);                        //Sends the population list and number of years to least number.

       lblLeastIncrease.Text = least.ToString();                                        //Assigns the least into the lblLeastIncrease.
    }

调用其他方法来整理数据：Average 是超前的。但是 GreatestIncrease 和 LeastIncrease 正在搜索数据列表（假设它已经从最早到最新排序，这是一个糟糕的假设，如果你问我......）以确定哪一年（或实际上是列表索引）包含最大的变化（或最小的变化，在 LeastIncrease 的情况下）。

方法名称给出的不好，并且不能很好地传达它返回的数据。如果我正在查看此代码，我建议将方法名称分别更改为“GetIndexOfGreatestIncrease”和“GetIndexOfLeastIncrease”。

    private int GreatestIncrease(List<int> PopulationList)                              //Imports the population list to Greatest.

    {
        int amountOfChange = 0;
        int changeInYears = 0;
        int i;
        int theChange = 0;
        int currentYear = 0;

        for (i = 1; i < PopulationList.Count(); i++)
        {
            theChange = PopulationList[i] - PopulationList[i - 1];
            currentYear = i;

            if (theChange > amountOfChange)
            {
                amountOfChange = theChange;
                changeInYears = i;
            }
        }

        return changeInYears;
    }

    private int LeastIncrease(List<int> PopulationList)                                 //Imports the population list to Least.
    {
        int firstItem = PopulationList.First();
        int lastItem = PopulationList.Last();

        int amountOfChange = (lastItem - firstItem);
        int changeInYears = 0;
        int i;
        int theChange = 0;
        int CurrentYear = 0;

        for (i = 1; i < PopulationList.Count(); i++)
        {
            theChange = PopulationList[i] - PopulationList[i - 1];
            CurrentYear = i;

            if (theChange < amountOfChange)
            {
                amountOfChange = theChange;
                changeInYears = i;
            }
        }

        return changeInYears;
    }

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于 2013-09-26T17:39:22.420 回答