我试图根据用户选择 2 文件来排序文件。 我正使用字符串变量并将其传送到 instream ()
中, 但是它不断进入 if
语句, 上面写着文件是腐败的还是不存在的。 我知道它存在, 因为当我在其中硬编码文件名称时, 它的功能完全正常! 我确信它很简单, 但我无法解开它。 我非常新到 c+++, 所以请对您的答案保持透彻, 以便我能理解和学习。 谢谢! 提前感谢!
#include <iterator>
#include <algorithm>
#include <vector>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
std::string file = "";
std::ofstream out("outputfile.txt");
std::vector<int> numbers;
std::string sortType = "";
void sort(std::vector<int>);
void MergeSort(vector<int> &numbers);
int main()
{
std::cout << "Which type of sort would you like to perform(sort or mergesort)?
";
std::cin >> sortType;
std::cout << "Which file would you like to sort?
";
std::cin >> file;
std::ifstream in(file);
//Check if file exists
if(!in)
{
std::cout << std::endl << "The File is corrupt or does not exist! ";
return 1;
}
// Read all the ints from in:
std::copy(std::istream_iterator<int>(in), std::istream_iterator<int>(),
std::back_inserter(numbers));
//check if the file has values
if(numbers.empty())
{
std::cout << std::endl << "The file provided is empty!";
return 1;
} else
{
if(sortType == "sort")
{
sort(numbers);
}else
{
MergeSort(numbers);
}
// Print the vector with tab separators:
std::copy(numbers.begin(), numbers.end(),
std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
// Write the vector to a text file
std::copy(numbers.begin(), numbers.end(),
std::ostream_iterator<int>(out, " "));
std::cout << std::endl;
}
return 0;
}
void sort(std::vector<int>)
{
// Sort the vector:
std::sort(numbers.begin(), numbers.end());
std::unique(numbers.begin(), numbers.end());
return;
}
vector<int> Merge(vector<int> &left, vector<int> &right)
{
std::vector<int> result;
while (left.size() > 0 && right.size() > 0)
{
if (left[0] <= right[0])
{
result.push_back(left[0]);
left.erase(left.begin());
} else
{
result.push_back(right[0]);
right.erase(right.begin());
}
}
if (left.size() > 0)
{
result.insert(result.end(), left.begin(), left.end());
} else
{
result.insert(result.end(), right.begin(), right.end());
}
return result;
}
void MergeSort(vector<int> &numbers)
{
if (numbers.size() <= 1)
{
return;
}
// split vector into two peices
vector<int> left, right;
unsigned int Middle = numbers.size() / 2;
for (unsigned int i = 0; i < Middle; i++)
{
left.push_back(numbers[i]);
}
for (unsigned int i = Middle; i < numbers.size(); i++) {
right.push_back(numbers[i]);
}
MergeSort(left);
MergeSort(right);
numbers = Merge(left, right);
return;
}