Question

以下程序是库存菜单。出于某种原因，除了搜索产品名称（选项3）函数lookupName之外，一切似乎都有效。它在我将一个条件放到哪里，如果没有返回任何内容之前正在工作，给出一个错误消息，这与我用于lookupSku的情况相同，并且一个正常工作。我不确定代码有什么问题。

#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstdlib>


using namespace std;

struct inventory {

  string name;
  int sku;
  int quantity;
  double price;
};

int size = 0;

void fillArray ( inventory[], int&, ifstream& );
void sortArray ( inventory[], int );
void displayIn ( inventory[], int );
int lookupSku ( inventory[], int, int );
int lookupName ( inventory[], int, string );

int main(){
  // Constants for menu choices
  const int DISPLAY_INVENTORY = 1,
            LOOKUP_SKU = 2,
            LOOKUP_NAME = 3,
            QUIT_CHOICE = 4;

  int choice;

  inventory products [100];

  ifstream fin;
  fin.open ("inventory.dat");

  if (!fin)
  {
    cout << endl << endl
         << " ***Program Terminated. *** " << endl << endl
         << " Input file failed to open. " << endl;

    system ( "PAUSE>NUL" );

    return 1;
  }

  fillArray ( products, size, fin );
  sortArray ( products, size );

   // Set up numeric output formatting.
   cout << fixed << showpoint << setprecision(2);

   do
   {
      // Display the menu.
      cout << "\n\t\t Manage Inventory Menu\n\n"
           << "1. Display inventory sorted by sku\n"
           << "2. Lookup a product by sku\n"
           << "3. Lookup a product by name\n"
           << "4. Quit the Program\n\n"
           << "Enter your choice: ";
      cin >> choice;
      cout << endl;

      // Validate the menu selection.
      while (choice < DISPLAY_INVENTORY || choice > QUIT_CHOICE)
      {
         cout << "Please enter a valid menu choice: ";
         cin >> choice;
      }

      // Validate and process the user's choice.
      if (choice != QUIT_CHOICE)
      {
         int indexSku,
             indexName,
             skuChoice;

         string nameChoice;

         switch (choice)
         {
            case DISPLAY_INVENTORY:
                displayIn ( products, size );
            break;

            case LOOKUP_SKU:
                cout << "Enter the Sku number: ";
                cin >> skuChoice;
                cout << endl;

                indexSku = lookupSku( products, size, skuChoice );

                if ( indexSku >= 0 )
                {
                  cout << "Product Name: " << products[indexSku].name << endl
                       << "Sku: " << products[indexSku].sku << endl
                       << "Quantity: " << products[indexSku].quantity << endl
                       << "Price: " << products[indexSku].price << endl;
                }
                else
                  cout << "No product found with this sku!" << endl;

            break;

            case LOOKUP_NAME:
                cout << "Enter product name with no spaces: ";
                cin >> nameChoice;
                cout << endl;

                indexName = lookupName( products, size, nameChoice );

                if ( indexName >= 0 )
                {
                  cout << "Product Name: " << products[indexName].name << endl
                       << "Sku: " << products[indexName].sku << endl
                       << "Quantity: " << products[indexName].quantity << endl
                       << "Price: " << products[indexName].price << endl;
                }
                else
                  cout << "No product found with this product name!" << endl;

            break;
         }

      }
   } while (choice != QUIT_CHOICE);

 fin.close ();

 return 0;
}

void fillArray ( inventory product[], int &size, ifstream &fin )
{
  int counter = 0;

  while (fin >> product[counter].name)
  {
     fin >>  product[counter].sku>> product[counter].quantity
         >> product[counter].price;

     counter ++;
  }

  size = counter;
}

void sortArray ( inventory product[], int size )
{
   bool swap;

   do
   {
      swap = false;
      for (int count = 0; count < (size - 1); count++)
      {
         if ( product[count].sku > product[count + 1].sku )
         {
            inventory temp = product[count];
            product[count] = product[count + 1];
            product[count + 1] = temp;

            swap = true;
         }
      }
   } while (swap);
}


void displayIn ( inventory product[], int size )
{
  for ( int i = 0; i < size; i++ )

  cout << product[i].sku << "    " <<  product[i].quantity << "     "
       <<  product[i].price << "    " << setw(4) <<  product[i].name << endl;
}

int lookupSku(inventory product[], int size, int value)
{
   int first = 0,
       last = size - 1,
       middle,
       position = -1;
   bool found = false;

   while (!found && first <= last)
   {
      middle = (first + last) / 2;
      if (product[middle].sku == value)
      {
         found = true;
         position = middle;
      }
      else if (product[middle].sku > value)
         last = middle - 1;
      else
         first = middle + 1;
   }
   return position;
}

int lookupName ( inventory product[], int size , string value )
{
   int first = 0,
       last = size - 1,
       middle,
       position = -1;
   bool found = false;

   while (!found && first <= last)
   {
      middle = (first + last) / 2;
      if (product[middle].name == value)
      {
         found = true;
         position = middle;
      }
      else if (product[middle].name > value)
         last = middle - 1;
      else
         first = middle + 1;
   }
   return position;
}

Answer 1

使用二进制搜索查找产品名称的代码是正确的，但似乎数据按SKU排序。二进制搜索算法仅在数据排序时才有效。

您可以在应用二进制搜索之前修改您的程序以按产品名称对数据进行排序，但在这种情况下，由于您使用的冒泡排序是N ^ 2搜索时间，因此您最好只使用线性搜索搜索产品名称。

二进制搜索字符串无法正常工作

1 个答案: