Sort by Last Name

[lkdodd]

I am trying to sort a dynamically allocated array of structures alphabetically by last name. In order to do that I have to get the last name from the fullName character array so that I can compare them. Does anyone know an easier way I can accomplish this? I am not getting "errors" per se, but I am getting a lot of warnings and it's not letting me compile the program.

void SortRecords(CustomerAccountRecords* ptr, int SIZE)
{
	char lastName1[50], lastName2[50];
	for (int start = 0; start < SIZE; start++) {
		int minIndex = start;
		for (int i = start + 1; i < SIZE; i++) {
			lastName1[50] = GetLastName(ptr, i);
			lastName2[50] = GetLastName(ptr, minIndex);
			if (strcmp(lastName1, lastName2) < 0)
				minIndex = i;
		}
		swap(ptr[minIndex], ptr[start]);
	}
}

char GetLastName(CustomerAccountRecords* ptr, int recordNum)
{
	char lastName[50];

	for (int i = 0; i < strlen(ptr[recordNum].fullName); i++) {
		if (isspace(ptr[recordNum].fullName[i])) {
			for (int j = i + 1; j < strlen(ptr[recordNum].fullName); j++) {
				lastName[j - (i + 1)] = ptr[recordNum].fullName[j];
			}
		}

	}
}

[lkdodd]

I've changed it now to:

void SortRecords(CustomerAccountRecords* ptr, int SIZE)
{
	char lastName1[50], lastName2[50];
	for (int start = 0; start < SIZE; start++) {
		int minIndex = start;
		for (int i = start + 1; i < SIZE; i++) {
			GetLastName(ptr, i, lastName1);
			GetLastName(ptr, minIndex, lastName2);
			if (strcmp(lastName1, lastName2) < 0)
				minIndex = i;
		}
		swap(ptr[minIndex], ptr[start]);
	}
}

char GetLastName(CustomerAccountRecords* ptr, int recordNum, char *lastName)
{
	for (int i = 0; i < strlen(ptr[recordNum].fullName); i++) {
		if (isspace(ptr[recordNum].fullName[i])) {
			for (int j = i + 1; j < strlen(ptr[recordNum].fullName); j++) {
				lastName[j - (i + 1)] = ptr[recordNum].fullName[j];
			}
		}

	}
}

[JLBorges]

#include <iostream>
#include <string>
#include <cctype>
#include <cstring>
#include <algorithm>

struct customer
{
    // consider using std::string to hold the full name
    // string: https://cal-linux.com/tutorials/strings.html
    static const int NAME_SZ = 127 ;
    char full_name[NAME_SZ+1] {} ;
    // other stuff
};

// string: https://cal-linux.com/tutorials/strings.html
std::string first_name( const customer& cust )
{
    std::string fname ;

    const char* p = cust.full_name ;
    while( *p != 0 && std::isspace(*p) ) ++p ; // skip leading spaces

    for( ; *p != 0 && !std::isspace(*p) ; ++p ) fname += *p ; // add characters of first name

    return fname ;
}

std::string last_name( const customer& cust )
{
    std::string lname ;

    // get to the last character in the c string
    const char* p = cust.full_name + std::strlen( cust.full_name ) - 1 ;

    while( *p > cust.full_name && std::isspace(*p) ) --p ; // skip trailing spaces

    for( ; p >= cust.full_name && !std::isspace(*p) ; --p ) lname += *p ; // add characters of last name

    // the characters have been added from right to left, so reverse it
    std::reverse( lname.begin(), lname.end() ) ;

    return lname ;
}

// considr using std::vector if the items are to be dynamically allocated
// vector: https://cal-linux.com/tutorials/vectors.html
// https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rsl-arrays

// get the index of the customer with the smallest last name
int min_index( const customer* cust, int sz ) // note: case sensitive
{
    int min_pos = 0 ;

    for( int i = 1 ; i < sz ; ++i )
        if( last_name( cust[i] ) < last_name( cust[min_pos] ) ) min_pos = i ;

    return min_pos ;
}

void sort_on_last_name( customer* cust, int sz ) // note: case sensitive
{
    if( sz > 1 ) // if there is more than one item left
    {
        // get the position of the item that should appear right in front
        const int min_pos = min_index( cust, sz ) ;

        // bring that item to the front
        using std::swap ;
        if( min_pos != 0 ) swap( cust[0], cust[min_pos] ) ;

        // sort the remaining sz-1 items
        sort_on_last_name( cust+1, sz-1 ) ;
    }
}

void std_sort_on_first_name( customer* cust, int sz ) // note: case sensitive
{
    // lambda expression: http://www.stroustrup.com/C++11FAQ.html#lambda
    // auto: http://www.stroustrup.com/C++11FAQ.html#auto
    const auto cmp_first_name = [] ( const customer& a, const customer& b )
    { return first_name(a) < first_name(b) ; };

    // https://en.cppreference.com/w/cpp/algorithm/sort
    std::sort( cust, cust+sz, cmp_first_name ) ;
}

int main() // minimal test driver
{
    customer cust[] =
    {
        { " Bjarne Stroustrup" },
        { "Andrew Richard Koenig " },
        { "  Alexander Stepanov  " },
        { "David Abrahams" },
        { "Dennis Ritchie" },
        { " Alan Mathison Turing " },
        { "Adele Goldberg" },
    };

    const int N = sizeof(cust) / sizeof(cust[0]) ;

    sort_on_last_name( cust, N ) ;

    // range based loop
    // http://www.stroustrup.com/C++11FAQ.html#for
    for( const customer& c : cust ) std::cout << last_name(c) << ", "  << first_name(c) << '\n' ;

    std::cout << "\n-----------\n\n" ;

    std_sort_on_first_name( cust, N ) ;
    for( const customer& c : cust ) std::cout << first_name(c) << ' ' << last_name(c) << '\n' ;
}

http://coliru.stacked-crooked.com/a/93ed5f2919e82e8d

[Handy Andy]

Hello lkdodd,

I do not know if using a character array is required or if you could use a "std::string" in it place. Using "std::string" can solve a lot of your problems.

I put this together to test it out, nut you may find it useful:

#include <iostream>
#include <limits>
#include <string>

int main()
{
	size_t pos{}; // <--- Can be done with out this variable
	std::string fullName/*{ "De Laurentiis, Giada" }*/; // <--- Remove comments for testing.
	std::string firstName, lastName;

	std::cout << "\n Enter full name (Last, First): ";
	std::getline(std::cin, fullName); // <--- Comment out for testing.

	pos = fullName.find(',', 0);

	lastName = fullName.substr(0, pos);
	firstName = fullName.substr(pos + 2); // <--- Starting position is past the "," and space.

	 // <--- Can also be written as:
	//lastName = fullName.substr(0, fullName.find(',', 0)); // <--- Negate the need for "pos".
	//firstName = fullName.substr(fullName.find(',', 0) + 2);  // <--- Moves past the comma and space.

	std::cout << "\n\n  Last Name: " << lastName << std::endl;
	std::cout << " First Name: " << firstName << std::endl;


	// The next line may not be needed. If you have to press enter to see the prompt it is not needed.
	//std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>.
	std::cout << "\n\n Press Enter to continue :";
	std::cin.get();

	return 0;
}

I did all of this in "main", but you could just as easily put this in a function. There are two ways to use ".find". Either way works.

Should you need to use character arrays. Look to what JLBorges did.

Hope that helps,

Andy