Selection Sort and String

[Saint48198]

I'm having trouble with a program. The program needs to do a selection sort of last names. I have the program sorting the names correctly, but I can not get the correct first name to appear next to its last name. I've tried a loop and either get the same name or an incorrect name. The code and data follows.

#include <fstream>
#include <string>
#include <iomanip>
#include <iostream>

using namespace std;

void sortData(string lName[], int noOfRows);

int main ()
{
	// step 1
	string lName[15];
	string fName;
	int age, wTime, i = 0, j, k, num = 0;
	char sex;
	ifstream inFile; // input stream variable for data file
	ofstream outFile; // output stream variable for result data

	inFile.open("data.txt");

	if (!inFile) // step 3
	{
		cout << "Cannot open the input file." << endl;
		return 1;
	}

	outFile.open("results.txt");// step 4

	while (!inFile.eof())
	{
		inFile >> fName >> lName[i++] >> age >> sex >> wTime;
	}
	
	sortData(lName, i);
	
	for (k = 0; k < i; k++)
	{
		outFile << lName[k] << " " << endl;
		outFile << fName << endl;
	}
	return 0;
}


void sortData(string lName[], int noOfRows)
{
	int i, j;
	int min;

	// selection sort
	for (i = 0; i < noOfRows - 1; i++)
	{
		// step a
		min = i;

		for (j = i + 1; j < noOfRows; j++)
			if (lName[j] < lName[min])
				min = j;

		
		if(min!=i)// step b
		lName[i].swap(lName[min]);
	}
}

Michael Brooks 13 M 33
Amy Shields 30 F 40
Clara Miles 50 F 30
Robert Davidson 20 M 45
Joshua Chase 25 M 42
Jackie Choker 20 F 29
Sarla Kothari 60 F 37
George Runner 53 M 49
Sally Jones 19 F 47

[Ancient Dragon]

Did you post your exact program? Because the code you posted doesn't fit the results you posted.

>>inFile >> fName >> lName[i++] >> age >> sex >> wTime;

lName array is ok, but on every iteration of that loop the program just simply overwrites whatever was read on the previous loop for the other variables. I'd suggest you use a structure to contain all the information, then sort the structures.

struct person
{
   string lName;
   string fName;
   int age;
   // etc etc
};

struct person array[MaxPeople];

//put the next two lines inside the read-data loop.
nFile >> array[i].fName >> array[i].lName>> array[i].age >> array[i].sex >> array[i].wTime;
++i;

Now all you have to do is use selection sort to sort the structures by last name. use memcpy() to exchange the entire structure, not just the individual elements of the structure will make it work faster.

[Lerner]

If you aren't allowed to use struct/classes to this as suggested by Ancient Dragon, then it can be done by using parallel arrays. This type of problem seems to be commonly assigned by instructors as a mechanism to get you working with arrays and as a mechanism to get you thinking in a problem solving mode. In particular if you had two arrays, one with last names and one with first names and each first name is related to the last name with the same index and you sort the last name array, how would you assure that the first names are changed at the same time so they remain assoicated with the correct last name?

[Saint48198]

I think I understand the parallel array, but I can't get the first name to stay with the correct last name. The parallel array is based on the i variable. but some how the first name still does not stay where it needs to be. I think I may need to add the fName variable to the sort function. Your also correct, I can not use struct in this program. I wish I could I understand it better.

#include <fstream>
#include <string>
#include <iomanip>
#include <iostream>

using namespace std;

void sortData(string lName[], string fName[], int noOfRows);

int main ()
{
	// step 1
	string lName[15];
	string fName[15];
	int age, wTime, i = 0, j, k, num = 0;
	char sex;
	ifstream inFile; // input stream variable for data file
	ofstream outFile; // output stream variable for result data

	inFile.open("data.txt");

	if (!inFile) // step 3
	{
		cout << "Cannot open the input file." << endl;
		return 1;
	}

	outFile.open("results.txt");// step 4

	while (!inFile.eof())
	{
		inFile >> fName[i] >> lName[i] >> age >> sex >> wTime;
		i++;
	}
	sortData(lName, fName, i);

	for (i = 0; i < 15; i++)
	{
		outFile << lName[i] << " " << fName[i] << endl;
	}
	
	return 0;
}


void sortData(string lName[], string fName[], int noOfRows)
{
	int i, j;
	int min;

	// selection sort
	for (i = 0; i < noOfRows - 1; i++)
	{
		// step a
		min = i;

		for (j = i + 1; j < noOfRows; j++)
			if (lName[j] < lName[min])
				min = j;

		if(min!=i)// step b
		lName[i].swap(lName[min]);
	}
}

[Saint48198]

I got it, thanks for the help.

[Saint48198]

I need a little more help on this program.

I need to determine the fitness level of the people in the file. I wrote a function that returns a int value based on thier fitness level. This worked fine with the normal loop, but now the code can not determine between the different record sets.

#include <fstream>
#include <string>
#include <iomanip>
#include <iostream>

using namespace std;

int cal_Fitness_Level(int age[], char sex[], int wTime[]);
void sortData(string lName[], string fName[], int age[], char sex[], int wTime[], int noOfRows);

int main ()
{
	// step 1
	string lName[15];
	string fName[15];
	int age[15], wTime[15], i = 0, level, num = 0;
	char sex[15];
	ifstream inFile; // input stream variable for data file
	ofstream outFile; // output stream variable for result data

	inFile.open("data.txt");

	if (!inFile) // step 3
	{
		cout << "Cannot open the input file." << endl;
		return 1;
	}

	outFile.open("results.txt");// step 4

	outFile << setfill(' ') << left << setw(15) << "Last Name" //header for output file
		<< setfill(' ') << left << setw(22) << "First Name" 
		<< setfill(' ') << left << setw(7) << "Age" 
		<< setfill(' ') << left << setw(7) << "Gender" 
		<< setfill(' ') << left << setw(10) << "Walk Time" 
		<< setfill(' ') << left << setw(13) << "Fitness Level" << endl;

	while (!inFile.eof())
	{
		inFile >> fName[i] >> lName[i] >> age[i] >> sex[i] >> wTime[i]; // step 5
		i++;
		level = cal_Fitness_Level(age, sex, wTime);// step 6
		num++;
	}
	
	sortData(lName, fName, age, sex, wTime, i);// step 7
	
	for (i = 0; i < 9; i++)// step 8
	{
		outFile << setfill(' ') << left << setw(15) << lName[i] 
		<< setfill(' ') << left << setw(22) << fName[i] 
		<< setfill(' ') << left << setw(9) << age[i] 
		<< setfill(' ') << left << setw(7) << sex[i] 
		<< setfill(' ') << left << setw(11) << wTime[i] 
		<< setfill(' ') << left << setw(7) << level << endl;
	}
	
	outFile << '\n' << "Number of records: " << num << endl;

	return 0;
}

int cal_Fitness_Level(int age[], char sex[], int wTime[])
{
	int fL;
	int i = 0;

	if (age[i] >= 13 && age[i] <= 19)
	{
		if (wTime[i] >= 48)
			fL = 1;
		else if (wTime[i] > 43 && wTime[i] <= 47)
			fL = 2;
		else if (wTime[i] > 39 && wTime[i] <= 43)
			fL = 3;
		else if (wTime[i] > 35 && wTime[i] <= 39)
			fL = 4;
		else if (wTime[i] < 35)
			fL = 5;
	}
	else
		fL = 0;

	return fL;
}

Michael Brooks 13 M 33
Amy Shields 30 F 40
Clara Miles 50 F 30
Robert Davidson 20 M 45
Joshua Chase 25 M 42
Jackie Choker 20 F 29
Sarla Kothari 60 F 37
George Runner 53 M 49
Sally Jones 19 F 47