Question

我有这个代码，我已经工作了几个小时，现在试图找出如何在插入排序期间实现删除排序数组中的重复项。我试图这样做而不必重新编写整个程序，但随着我的进步，似乎我可能只需要从头开始，但在此之前，我希望看看是否可以这样做下面的代码。

目前的问题是，如何在将重复数据放回文件之前从已排序的数组中删除副本？

#include <iostream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <vector>
using std::cout;
using std::endl;
using namespace std;

//sort into an array using insertion sort
//getis info from file "numbers.txt"
//and prints the sorted numbers into "sorted_numbers.txt"
void insertSort(int a[], int length)
{
   int i, j, value;
   int old = 0;
   bool first = true;

   for(i = 1; i < length; i++)
   {
       if(first || old != a[i])
       {
           old = a[i];
           first = false;

           value = a[i];
           for (j = i - 1; j >= 0 && a[j] > value; j--)
           {
               a[j + 1] = a[j];
           }
       }
       a[j + 1] = value;
   }
}

//prints out the array in 'Run I/O'
void printarray(int arg[], int length)
{
    for(int n =0; n<length; ++n)
      cout << arg[n] << ' ';
    cout << '\n';
}

int main ()
{
    std::ifstream in;
    std::ofstream out;

    int N = 10;
    int n = 0;
    int k;
    int* a = new int(N);

    //opens the file "numbers.txt" if it exit
    //gets the chars from file and sorts them 
    //into array "a[n]" 
    in.open("numbers.txt");
    if(!in.is_open())
    {
        std::cout << "File could not be opened FILE NOT FOUND." << std::endl;

        //creates the a new file to be read from if numbers.txt does
        //not already exist and put numbers inside of it
        //to be sorted with the InsertSort function
        out.open("numbers.txt");
        out << "1" << endl;
        out << "3" << endl;
        out << "7" << endl;
        out << "4" << endl;
        out << "2" << endl;
        out << "7" << endl;
        out << "6" << endl;
        out << "9" << endl;
        out << "5" << endl;
        out << "2" << endl;

        out.close();

        //opens the new numbers.txt file and puts the 
        //numbers into an array to be sorted
        in.open("numbers.txt");

        //runs through the items in the file and
        //puts them into an array
        int x;
        while(in >> x) 
        {
            a[n] = x;
            n++; 
        }

        printarray(a,10);
        std::cout << "Read " << n << " integers from the file." << std::endl;

        //sorts the array from when it was read 
        //to the new insertion sort array
        insertSort(a,n);

        std::cout << "Integers are sorted" << std::endl;

        //writes/creates the new sorted array to a new file
        //called "sorted_numbers.txt"
        out.open("sorted_numbers.txt");
        for(k = 0;k < n;k++)
            out << a[k] << std::endl;
            printarray(a,10);
        out.close();

        delete[] a;

        in.close();
    }
    else
    {
        int x;
        while(in >> x) 
        {
            a[n] = x;
            n++;
         }

      printarray(a,10);
      std::cout << "Read " << n << " integers from the file." << std::endl;

      insertSort(a,n);

      std::cout << "Integers are sorted" << std::endl;

      //writes/creates the new sorted array to a new file
      //called "sorted_numbers.txt"
      out.open("sorted_numbers.txt");
      for(k = 0;k < n;k++)
          out << a[k] << std::endl;   
          std::cout << n << " integers stored to the file." << std::endl;
          printarray(a,10);
      out.close();

      delete[] a;
   }
   return 0;
}

Answer 1

插入排序从左向右操作并将子数组向右旋转（将最小值放在子数组的左侧），而删除副本则将子数组向左移动。作为替代方案，我创建并修改了一个＆＃34;删除＆＃34; sort（反向插入排序），从右到左操作并将子数组向左旋转（将最大值放在子数组的右侧），并将子数组左移以删除重复项。 / p>

void deletesort(int a[], int &length)
{
    int i, j, value;
    if(length < 2)
        return;
    for(i = length-2; i >= 0; i--){
        value = a[i];
        for (j = i+1; j < length; j++){
            if(value > a[j]){
                a[j-1] = a[j];
                continue;
            }
            if(value == a[j]){
                for( ; j < length; j++)
                    a[j-1] = a[j];
                length--;
            }
            break;
        }
        a[j-1] = value;
    }
}

这是一个删除排序，不会删除重复项：

void deletesort(int a[], int length)
{
    int i, j, value;
    if(length < 2)
        return;
    for(i = length-2; i >= 0; i--){
        value = a[i];
        for (j = i+1; j < length && value > a[j]; j++)
            a[j-1] = a[j];
        a[j-1] = value;
    }
}

Answer 2

使用algorithm库和std::vector

#include <algorithm>
#include <vector>
#include <fstream>

int main()
{
  std::vector<int> v;
  {
    std::ifstream is("numbers.txt");
    for (int i; is >> i; )
      v.push_back(i);
  }

  std::sort(v.begin(), v.end());
  v.erase(std::unique(v.begin(), v.end()), v.end());

  std::ofstream of("sorted_numbers.txt");
  for (auto i : v)
    of << i << '\n';

  // Or for non-c++11
  // for (std::vector<int>::const_iterator i = v.begin(); i != v.end(); ++i)
  //   of << *i << '\n';
}

或者为了简单起见甚至是std::set（矢量版本可能更快，但可能对您的用例而言并不重要。）

#include <algorithm>
#include <set>
#include <fstream>

int main()
{
  std::set<int> s;
  {
    std::ifstream is("numbers.txt");
    for (int i; is >> i; )
      s.insert(i);
  }

  std::ofstream of("sorted_numbers.txt");
  for (auto i : s)
    of << i << '\n';

  // Or for non-c++11
  // for (std::set<int>::const_iterator i = s.begin(); i != s.end(); ++i)
  //   of << *i << '\n';
}

从已排序的数组中删除重复项

2 个答案: