C ++按字母顺序对名称进行排序

Question

I have a program that is trying to sort some names alphabetically. I run it and it does not have any errors, but the names are not sorted. I compare 2 names and see which one is supposed to be shifted in the array.

Here is the code:

void sort_names(char array[])
{
    const int arraysize = 5;

    // Step through each element of the array
    for (int startindex = 0; startindex < arraysize; startindex++)
    {

        int smallestnum = startindex;

        for (int currentindex = startindex + 1; currentindex < arraysize; currentindex++)
        {
            // If the current element is smaller than our previously found smallest
            if ((student_list[currentindex].lname) < (student_list[smallestnum].lname))
            // Store the index 
            smallestnum = currentindex;
        }

        // Swap our start element with our smallest element
        swap(student_list[startindex], student_list[smallestnum]);
    }
}

My struct looks like this:

struct student {
    char fname[30]; 
    char lname[30];
};

Do I have to convert these to strings somewhere because they are characters arrays? I am kind of lost and trying to figure out how to make it sort properly.

Answer 1

The Problem is that in this line:

if ((student_list[currentindex].lname) < (student_list[smallestnum].lname))

it doesn't compare string characters, but rather compares memory adresses.

If you still want to use char arrays, you have to use the strcmp function. However, I recommed that you use string instead.

Answer 2

The problem is this line:

if ((student_list[currentindex].lname) < (student_list[smallestnum].lname))

The line compares the pointers, it does not compare the contents.

It should be:

if ( strcmp( student_list[currentindex].lname, student_list[smallestnum].lname ) < 0 )

Another alternative is to use std::string instead, which has built-in comparisons. For example:

struct student {
    std::string fname; 
    std::string lname;
};