我试图按字母顺序对2元素数据结构的数组进行排序。整个程序将数据文件读入数组，然后按字母顺序排列数组并按查询搜索。
我的问题是在排序后清除数据库的第一个条目。这可以在本文末尾的输出中看到。
代码如下
#include <iostream> //Required if your program does any I/O
#include <fstream> //Required for file I/O
#include <string> //Required if your program uses C++ strings
using namespace std; //Required for ANSI C++ 1998 standard.
struct Book // Data structure of database entry
{
string title;
string author;
};
const int ARRAY_SIZE = 1000; //Maximum database size
Book books [ARRAY_SIZE]; //Library database
void loadData ( int& librarySize ); //Function prototype to load data file into database
void showAll ( int librarySize ); //Function prototype to display entire database contents
void menu ( int librarySize ); //Function prototype to process menu of database functions
void searchByAuthor ( int librarySize ); //Function prototype to search database by author
void searchByTitle ( int librarySize ); //Function prototype to search database by title
void sortByAuthor ( int librarySize ); //Function prototype to alphabetically sort database by author
void sortByTitle ( int librarySize ); //Function prototype to alphabetically sort database by title
int main ()
{
int librarySize = 0; //Declaring and initializing databse size variable
cout << "Welcome to Greathouse's Library Database" << endl;
loadData ( librarySize ); //Prompt for and loading of data file into database.
menu ( librarySize ); //Processing of database functions menu
system("pause");
exit(0);
}
void loadData ( int& librarySize )
{
ifstream inputFile; //File I/O variable
string inputFileName; //Data file path
//Prompt for data file path
cout << "Please enter the name of the backup file: ";
getline(cin, inputFileName);
// Open the data file.
inputFile.open(inputFileName.c_str()); // Need .c_str() to convert a C++ string to a C-style string
// Check the file opened successfully.
if ( ! inputFile.is_open())
{
cout << "Unable to open input file." << endl;
system("pause");
exit(-1);
}
//Read data file into database
for ( librarySize = 0; inputFile.peek() != EOF && librarySize < ARRAY_SIZE ; librarySize++ )
{
getline( inputFile, books[librarySize].title );
getline( inputFile, books[librarySize].author );
}
//Confirm number of records loaded with user
cout << librarySize << " records loaded successfully." << endl;
// Clear EOF flag on file stream
inputFile.clear();
// Return to the beginning of the file stream
inputFile.seekg(0);
}
void menu ( int librarySize )
{
char command = ' ';
//Display and processing of menu and commands until escape character 'q' is entered
while ( command != 'Q' && command != 'q' )
{
cout << "Would you like to (Q)uit, (S)howall, Search by (A)uthor, or Search by (T)itle? : ";
cin >> command;
switch ( command )
{
case 'S':
case 's':
showAll ( librarySize ); //Call to function to show database contents in response to user input
break;
case 'A':
case 'a':
searchByAuthor ( librarySize ); //Call to function to search database by author and display results alphabetically in response to user input
break;
case 'T':
case 't':
searchByTitle ( librarySize ); //Call to function to search database by title and display results alphabetically in response to user input
break;
case 'Q':
case 'q':
break; //Case option to prevent extraneous output when quitting program
default:
cout << "That is not a valid command." << endl;
break;
}
}
}
void searchByAuthor ( int librarySize ) //Function to search database by author
{
string authorSearch = " "; //User query
int authorResults = 0; //Number of query results found
int iteration = 0; //Loop counting variable
//Prompt for and reading of user query
cout << "Author: : ";
cin >> authorSearch;
sortByAuthor ( librarySize ); //Call to sort database alphabetically by author so output will be alphabetical
//Iterative search of database for all instances of query
for ( iteration = 0; iteration <= librarySize; iteration++ )
{
if ( books[iteration].author.find ( authorSearch ) != string::npos )
{
cout << books[iteration].title << " (" << books[iteration].author << ")" << endl;
authorResults++;
}
}
cout << authorResults << " records found." << endl; //Output of number of results
}
void searchByTitle ( int librarySize )
{
string titleSearch = " "; //User query
int titleResults = 0; //Number of query results found
int iteration = 0; //Loop counting variable
//Prompt for and reading of user query
cout << "Title: ";
cin >> titleSearch;
sortByTitle ( librarySize ); //Call to sort database alphabetically by title so output will be alphabetical
//Iterative search of database for all instances of query
for ( iteration = 0; iteration <= librarySize; iteration++ )
{
if ( books[iteration].title.find ( titleSearch ) != string::npos )
{
cout << books[iteration].title << " (" << books[iteration].author << ")" << endl;
titleResults++;
}
}
cout << titleResults << " records found." << endl; //Output of number of results
}
void showAll ( int librarySize ) //Function to show database contents
{
//Iterative walk through database to display contents
for ( int iteration = 0; iteration < librarySize; iteration++ )
{
cout << books[iteration].title << " (" << books[iteration].author << ")" << endl;
}
}
void sortByAuthor ( int librarySize ) //Function to sort database alphabetically by author
{
//Bubble sort of databse alphabetically by author
for ( int pass = 0; pass < librarySize ; pass++ )
{
for ( int iteration = 0; iteration < librarySize - pass; iteration++ )
{
if ( books[iteration].author > books[iteration+1].author )
{
swap ( books[iteration] , books[iteration+1] );
}
}
}
}
void sortByTitle ( int librarySize ) //Function to sort database alphabetically by title
{
//Bubble sort of databse alphabetically by title
for ( int pass = 0; pass < librarySize ; pass++ )
{
for ( int iteration = 0; iteration < librarySize - pass; iteration++ )
{
if ( books[iteration].title > books[iteration+1].title )
{
swap ( books[iteration] , books[iteration+1] );
}
}
}
}
测试数据
Objects First with Java
Barnes and Kolling
Game Development Essentials
Novak
The Game Maker's Apprentice
Overmars
C++ Programming: From Problem Analysis...
Malik
C++ Programming Lab Manual
Scholl
Beginning LINUX Programming
Stones and Matthew
C++ Programming: Program Design Including...
D. S. Malik
C++ How to Program
Deitel and Deitel
Programming and Problem Solving with C++
Dale, Weems, Headington
Game Character Development with Maya
Ward
Developing Games in Java
Brackeen
C# Programming
Harvey, Robinson, Templeman, Watson
Java Programming
Farrell
Audio for Games
Brandon
错误输出
Welcome to Greathouse's Library Database
Please enter the name of the backup file: library.txt
14 records loaded successfully.
Would you like to (Q)uit, (S)howall, Search by (A)uthor, or Search by (T)itle? :
s
Objects First with Java (Barnes and Kolling)
Game Development Essentials (Novak)
The Game Maker's Apprentice (Overmars)
C++ Programming: From Problem Analysis... (Malik)
C++ Programming Lab Manual (Scholl)
Beginning LINUX Programming (Stones and Matthew)
C++ Programming: Program Design Including... (D. S. Malik)
C++ How to Program (Deitel and Deitel)
Programming and Problem Solving with C++ (Dale, Weems, Headington)
Game Character Development with Maya (Ward)
Developing Games in Java (Brackeen)
C# Programming (Harvey, Robinson, Templeman, Watson)
Java Programming (Farrell)
Audio for Games (Brandon)
Would you like to (Q)uit, (S)howall, Search by (A)uthor, or Search by (T)itle? :
t
Title: Game
Audio for Games (Brandon)
Developing Games in Java (Brackeen)
Game Character Development with Maya (Ward)
Game Development Essentials (Novak)
The Game Maker's Apprentice (Overmars)
5 records found.
Would you like to (Q)uit, (S)howall, Search by (A)uthor, or Search by (T)itle? :
s
()
Audio for Games (Brandon)
Beginning LINUX Programming (Stones and Matthew)
C# Programming (Harvey, Robinson, Templeman, Watson)
C++ How to Program (Deitel and Deitel)
C++ Programming Lab Manual (Scholl)
C++ Programming: From Problem Analysis... (Malik)
C++ Programming: Program Design Including... (D. S. Malik)
Developing Games in Java (Brackeen)
Game Character Development with Maya (Ward)
Game Development Essentials (Novak)
Java Programming (Farrell)
Objects First with Java (Barnes and Kolling)
Programming and Problem Solving with C++ (Dale, Weems, Headington)
Would you like to (Q)uit, (S)howall, Search by (A)uthor, or Search by (T)itle? :
答案 0 :(得分：1)
在大多数循环中，您使用以下条件：
iteration <= librarySize
您的数组索引范围从0到librarySize - 1（因为这些是loadData填充的索引），因此数组中的最后一个有效条目为books[librarySize - 1]。尝试将循环条件更改为：
iteration < librarySize
编辑：您的排序功能还有另一个问题：您正在尝试访问books[iteration+1]，这将在第一次通过时再次超出范围。你的内循环应该只到librarySize - pass - 1：
iteration < librarySize - pass - 1
答案 1 :(得分：0)
问题在于你的“泡沫”正在发生的地方。在两个循环中，从数组pos 0开始，当每个第一个元素位于正确的位置时，您需要向上移动。结尾永远不会被分类。
这是一些我没有测试过的代码，所以它可能会被1等关闭。但是你明白了
for ( int pass = 0; pass <= librarySize ; pass++ )
{
for ( int iteration = 0; iteration <= librarySize - pass; iteration++ )
{
if ( books[iteration+pass].title > books[iteration+pass+1].title )
{
swap ( books[iteration+pass] , books[iteration+pass+1] );
}
}
}
或者你可以这样做
for ( int pass = 0; pass <= librarySize ; pass++ )
{
for ( int iteration = pass; iteration <= librarySize ; iteration++ )
{
if ( books[iteration].title > books[iteration+1].title )
{
swap ( books[iteration] , books[iteration+1] );
}
}
}