C++ Selection Sorting String Arrays

Question

I'm trying to understand how selection sorting works with strings.

This is what I have so far:

#include <iostream>
#include <string>
using namespace std;


// Prototypes
void selectionSort(string arr[], int size);
void showArray(string arr[], int size);

int main() {
const int NUM_NAMES = 20;
string names[NUM_NAMES] = {"Collins, Bill", "Smith, Bart", "Allen, Jim",
                            "Griffin, Jim", "Stamey, Marty", "Rose, Geri",
                            "Taylor, Terri", "Johnson, Jill", "Allison, Jeff",
                            "Looney, Joe", "Wolfe, Bill", "James, Jean",
                            "Weaver, Jim", "Pore, Bob", "Rutherford, Greg",
                            "Javens, Renee", "Harrison, Rose", "Setzer, Cathy",
                            "Pike, Gordon", "Holland, Beth"};

// Insert your code to complete this program
cout << "The names on the list in no particlular order are: ";
showArray(names, NUM_NAMES);


// Calling the sorted array
selectionSort(names, NUM_NAMES);

// Displaying sorted array
cout << "The names in sorted order are: ";
showArray(names, NUM_NAMES);

return 0;
}

// Function to sort the string
void selectionSort(string arr[], int size) {
int startScan, minIndex, minValue;

for (startScan = 0; startScan < (size - 1); startScan++) {
    minIndex = startScan;
    minValue = arr[startScan];

    for (int index = (startScan + 1); index < size; index++) {
        if (arr[index] < minValue) {
            minValue = arr[index];
            minIndex = index;
        }
    }
    arr[minIndex] = arr[startScan];
    arr[startScan] = minValue;
    }

}

// Function to display the array's conents
void showArray(const int arr[], int size) {
    for (int count = 0; count < size; count++) {
        cout << arr[count];
        cout << "\t\n";
    }
}

If I try building it it fails and I get an error message. "No matching function for call to 'selectionSort'."

However, if I try and use ints instead of strings I'm able to get it to compile and sort properly.

#include <iostream>
#include <string>
using namespace std;


// Prototypes
void selectionSort(int [], int);
void showArray(const int [], int);

int main() {
const int NUM_NAMES = 8;
int names[NUM_NAMES] = {1,3,5,7,3,5,7,9};

// Insert your code to complete this program
cout << "The names on the list in no particular order are: ";
showArray(names, NUM_NAMES);


// Calling the sorted array
selectionSort(names, NUM_NAMES);

// Displaying sorted array
cout << "The names in sorted order are: ";
showArray(names, NUM_NAMES);

return 0;
}

// Function to sort the string
void selectionSort(int array[], int size) {
int startScan, minIndex, minValue;

for (startScan = 0; startScan < (size - 1); startScan++) {
    minIndex = startScan;
    minValue = array[startScan];

    for (int index = (startScan + 1); index < size; index++) {
        if (array[index] < minValue) {
            minValue = array[index];
            minIndex = index;
        }
    }
    array[minIndex] = array[startScan];
    array[startScan] = minValue;
    }

}

// Function to display the array's contents
void showArray(const int array[], int size) {
    for (int count = 0; count < size; count++) {
        cout << array[count];
        cout << "\t\n";
    }
}

I'm not quite sure where I'm going wrong with the string sorting. Image of c++ program with the portion that has an issue

Answer 1

The compile error is trivial. void selectionSort(int [], int); accepts array of integers, it sorts that array. But you want to sort array of strings. You have declared:

string names[NUM_NAMES];

You have to change the sort function to accept array of strings. The modification is rather easy since std::string supports =, <, >, == operators.

void selectionSort(string arr[], int size) 
{
    int startScan, minIndex;
    string minValue;

    for(startScan = 0; startScan < (size - 1); startScan++) 
    {
        minIndex = startScan;
        minValue = arr[startScan];

        for(int index = (startScan + 1); index < size; index++) 
        {
            if(arr[index] < minValue)
            {
                minValue = arr[index];
                minIndex = index;
            }
        }
        arr[minIndex] = arr[startScan];
        arr[startScan] = minValue;
    }
}