如何通过忽略单个字符的单独行来从文件中读取单独的整数行？

Question

我正在开发一个处理二叉搜索树的程序。我有一个简单的文本文件，如下所示：

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
$
5 4 3 5 7 13
$
11 6 7 2 12 6

第一行包含要插入树的整数，第三行是要搜索的整数，第五行是要删除的整数。第二行和第四行用于标记其他行的分隔。它们包含单个字符“$”。 我正在为如何忽略第二行和第四行而苦苦挣扎。我有三个 while 循环，用两个忽略语句分隔。经测试，似乎从未进入过第二个和第三个 while 循环。我将不胜感激 - 我的代码如下。

#include <iostream>
#include <cstdlib>
#include <string>
#include <fstream>
#include "main.h"


int main(int argc, char *argv[])
{    
    string filename = "";
    ifstream inFile;

    filename = argv[1];
    inFile.open(filename.c_str());

    BST b;
    int num;

    while(inFile >> num)
    {
       b.insert(num);
       cout << num << endl; //output testing - the first line was successfully output so I think this part is fine
    }

    inFile.ignore(500, '$');

    while(inFile >> num) //this while loop is never entered
    {
        b.search(num);
    }
    inFile.ignore(500, '\n');

    while(inFile >> num) //this while loop is never entered
    {
        b.remove(num);
    }

    inFile.close();  
}

Answer 1

当您完成读取数字的循环后，添加一行以清除输入流的错误状态。否则，不会执行后续的读取操作。

while(inFile >> num)
{
   b.insert(num);
   cout << num << endl; //output testing - the first line was successfully output so I think this part is fine
}

inFile.clear();           // ADD THIS LINE
inFile.ignore(500, '$');

while(inFile >> num) //this while loop is never entered
{
    b.search(num);
}

inFile.clear();           // ADD THIS LINE
inFile.ignore(500, '\n');