二进制搜索算法：数组中每条记录的文本文件

Posted 2023-03-30

【中文标题】二进制搜索算法：数组中每条记录的文本文件

【英文标题】：Binary Search Algorithm: Text File for each record in array

【发布时间】：2014-12-15 09:10:28

【问题描述】：

我有一个包含 90,000 个整数的数组，还有一个 txt 文件， 我必须按顺序读取txt文件，不允许将其放入数组中，Foreach记录在文本文件中 文件我必须使用二进制搜索在数组中找到相应的数字。然后显示有多少匹配数字。

我就是这样做的，但它只找到第一个匹配的数字然后停止

static void Main(string[] args)

    //etc(OTHER CODE).......................
    Array.Sort(NumFile);
    // BINARY SEARCHHHH
    int last,
    first,
    mid = 0,
    target,
    found = 0,
    counter = 0;
    string run;

    //Stats
    int Finds = 0;
    first = 0;
    last = NumFile.Length - 1;            
    //READ TextFile
    StreamReader search = new StreamReader("Records.txt");
    target = int.Parse(search.ReadLine());
    //while (last >= first && found == 0)
    while (last >= first && found == 0 && (run = search.ReadLine()) != null)
    
        mid = (last + first) / 2;
        if (target == NumFile[mid])
        
            found = 1;
        
        else
        
            if (target < NumFile[mid])
            
                 last = mid - 1;
            
            else
            
                 first = mid + 1;
            

        
        if (found == 1)
        
            Console.WriteLine("\nThe number was found at location 0", mid);
            Finds++;
        
        else
        
             //Console.WriteLine("\nNumber not found");                  
        

    

    Console.WriteLine("Binary Search Statistics \t Hits:0 ,hits);        

    .

【问题讨论】：

我不明白您为什么在二进制搜索循环中继续读取文件（进入“运行”）。它可能在寻找第一个数字时跳过了整个文件。我认为您需要两个嵌套循环：外部文件读取循环和内部搜索循环。

这是学校作业吗？你为什么不直接打电话给Array.BinarySearch？

【参考方案1】：

这是您的 while 循环，查看找到的 while 条件 == 0

while (last >= first && found == 0 && (run = search.ReadLine()) != null)

    mid = (last + first) / 2;
    if (target == NumFile[mid])
    
        found = 1;
    
    else
    
        if (target < NumFile[mid])
        
             last = mid - 1;
        
        else
        
             first = mid + 1;
        

    
    if (found == 1)
    
        Console.WriteLine("\nThe number was found at location 0", mid);
        Finds++;
    
    else
    
         //Console.WriteLine("\nNumber not found");                  
    

因此，在 where found == 1 if 语句中，您需要将 found 设置为 = 0，以便它在循环中继续

if (found == 1)

    Console.WriteLine("\nThe number was found at location 0", mid);
    Finds++;
    found =0;