从.txt文件

Question

我有一个看起来像这样的文本文件（但还有更多行）：

9527,88147
4963,75407
448P,34361
2545,29046
9095,258T8

如何找到第一列中所有数字的平均值？我知道如何找到平均值，但由于第1列中的一个数字中的P，我似乎无法使其工作。所以我如何在忽略chars的情况下找到平均值？

另外，如何在忽略char T的同时在第2列中找到最大数字？

以下是我计算平均值的代码：

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <algorithm>

using namespace std;

int main()
{
  ifstream file;
  string fileName;
  cout << "Please input the filename: ";
  cin >> fileName;
  file.open(fileName.c_str());
  while(file.fail())
  {
    file.clear();
    cout << "Incorrect filename, please input the filename: ";
    cin >> fileName;
    file.open(fileName.c_str());
  }

  // Calculate the average value of all numbers in the first column and the
  // largest value of all numbers in the second column 
  string line;
  long sum = 0;
  long i = 0;
  long max = 0;
  while (getline(file,line)) 
  {
    string str1, str2;

    size_t idx = line.find(",");
    str1 = line.substr(0,idx);
    str2 = line.substr(idx+1);

    str1.erase(std::remove_if(str1.begin (), str1.end (), ::isalpha), str1.end ());
    str2.erase(std::remove_if(str2.begin (), str2.end (), ::isalpha), str2.end ());

    int n;
    sum += stoi(str1); 
      n  = stoi(str2); 

    if(i == 0)
      max = n;
    else
    {
      if ( n > max )
        max = n;
    }

    ++i;
  }

  // The total number of rows in the file
  int rows = 0;
  {
    ++rows;
  }

  // Find the invalid numbers with letters in them and output them






  file.close();

  // Output of calculations
  cout.precision(4);
  cout << "The average value of all numbers in the first column: " << fixed << static_cast<double>(sum)/i << endl;
  cout << "The largest value of all numbers in the second column: " << max << endl;
  cout << "The total number of rows in the file is: " << i << endl;
  //cout << "The invalid numbers are: " << letters << endl;
  return 0;
}

我的平均值输出只是nan。

Answer 1

要删除字符，您可以使用erase()和isalpha来解决此问题。请参阅以下

#include <iostream>
#include <algorithm>
#include <fstream>
#include <string>
#include <iomanip> // std::setprecision
using namespace std;

int main()
{

    ifstream file("data.txt");
    string line;
    long sum = 0;
    long i = 0;
    long max = 0;
    while ( getline(file, line) ) {

        string str1, str2;

        size_t idx = line.find(",");
        str1 = line.substr(0,idx);
        str2 = line.substr(idx+1);

        str1.erase(std::remove_if(str1.begin (), str1.end (), isalpha), str1.end ());
        str2.erase(std::remove_if(str2.begin (), str2.end (), isalpha), str2.end ());

        int n;
        sum += stoi(str1); 
           n  = stoi(str2); 

        if( i == 0 )
            max = n;
        else{
            if ( n > max )
                max = n;
        }

        ++i;
    }

    cout.precision(4);
    cout << "average column 1: " << fixed << static_cast<double>(sum)/i << " and max column 2: " << max << endl;
}

txt文件是

1,1
2,2
3,3
4P,4
5,5T

，输出

average column 1: 3.0000 and max column 2: 5