Question

我想读一下文字档案中的图表紧急信息,将其储存成病媒。

档案有任意数量线
each line has arbitrary number of integers ended with

例如,

First line:
0 1 4
Second line:
1 0 4 3 2
Thrid line:
2 1 3
Fourth line:
3 1 2 4
Fifth line:
4 0 1 3

If I use getline() to read one line at a time, how do I parse the line (as each line has variable number of integers)?

任何建议?

Answer 1

标准行文:

#include <fstream>
#include <sstream>
#include <string>
#include <vector>


std::ifstream infile("thefile.txt");
std::string line;

while (std::getline(infile, line))
{
  std::istringstream iss(line);
  int n;
  std::vector<int> v;

  while (iss >> n)
  {
    v.push_back(n);
  }

  // do something useful with v
}

此处采用<条码>的单线版本。我们需要一个辅助性建筑(信用到@Luc Danton!) ,这与<代码”相反:move:



namespace std
{
  template <typename T> T & stay(T && t) { return t; }
}

int main()
{
  std::vector<std::vector<int>> vv;

  for (std::string line;
       std::getline(std::cin, line);
       vv.push_back(std::vector<int>(std::istream_iterator<int>(std::stay(std::istringstream(line))),
                                     std::istream_iterator<int>())
                    )
       ) { }

  std::cout << vv << std::endl;
}

Answer 2

第一行改为“<代码>std:getline function, 然后使用std:stringstream,改为:

std::ifstream file("input.txt");

std::vector<std::vector<int>> vv;
std::string line;
while(std::getline(file, line))
{
    std::stringstream ss(line);
    int i;
    std::vector<int> v;
    while( ss >> i ) 
       v.push_back(i);
    vv.push_back(v);
}

You can also write the loop-body as:

while(std::getline(file, line))
{
    std::stringstream ss(line);
    std::istream_iterator<int> begin(ss), end;
    std::vector<int> v(begin, end);
    vv.push_back(v);
}

这样做的时间越短,越好。或合并后两行:

while(std::getline(file, line))
{
    std::stringstream ss(line);
    std::istream_iterator<int> begin(ss), end;
    vv.push_back(std::vector<int>(begin, end));
}

现在,它不会缩短,因为它会ug。

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