Selection sorting strings on a struct

Question

#include <stdio.h>
#include <string.h>

void sort_names();


struct ListNames {

    char names[20];
    int age;

}n[6] = {

    {"Ryan, Elizabeth",62},
    {"McIntyre, Osborne",84},
    {"DuMond, Kristin",18},
    {"Larson, Lois",42},
    {"Thorpe, Trinity",15},
    {"Ruiz, Pedro",35},  

};

int main (void) {
    int i;
    printf("Original List");
    printf("\n-----------------------------");

    for (i = 0; i < 6; i++) {
        printf("\n%-20s",n[i].names);
        printf("      %2i",n[i].age);
    }


}

I am trying to sort the strings in the struct in alphabetical order, along with the int with the string. I am able to print it fine, but I am clueless on what to do next on calling the struct to sort it in alphabetical order. I know i am going to need an index value but I dont know how i would do that within a struct.

It's very simple: you just need to implement sort_names(); ;-) — P.P
– P.P, Commented Nov 25, 2014 at 19:57
@BlueMoon what do you mean sort_names() can you be more specific? — hello world
– hello world, Commented Nov 25, 2014 at 19:58
@BlueMoon I'm not following you dude.... implement that function onto n? — hello world
– hello world, Commented Nov 25, 2014 at 20:07
@hello world It would be better if the last and first names were separated that is would be stored in different character arrays. — Vlad from Moscow
– Vlad from Moscow, Commented Nov 25, 2014 at 20:12

Gaurav Sehgal · Accepted Answer · 2014-11-25 20:44:00Z

1

You can iterate over your entire list while keeping track of the smallest element.By smallest i mean by name.That element(name and age) is then swapped by the element at first position.Then the second smallest element is replace by element at second position in similar fashion.

int is_smaller(char *a,char *b)//returns true if a<b
{

if(strcmp(a,b)<0)
    return 1;
else
    return 0;
}
void swap(char* a,char* b)//to swap names
{
    char arr[100];
    strcpy(arr,a);
    strcpy(a,b);
    strcpy(b,arr);
}
void swap(int &a,int &b)//to swap age
{
    int temp=a;
    a=b;
    b=temp;
}  
int smallest;
for(int i=0;i<6;i++)
{
    smallest=i;
    for(int j=i+1;j<6;j++)
    if(!is_smaller(n[smallest].names,n[j].names))//is smaller return true if first argument is smaller than second
    {
        smallest=j;
    }
    if(smallest!=i)
    {
        swap(n[i].names,n[smallest].names);
        swap(n[i].age,n[smallest].age);
    }
}

edited Nov 25, 2014 at 20:44

answered Nov 25, 2014 at 20:05

Gaurav Sehgal

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3 Comments

hello world Over a year ago

it looks good, but I am confused on how to implement this? Ive tried adding this into my main function but no good.

hello world Over a year ago

thank you for updating, am i throwing all of this into the main function? sorry for the late response!

Gaurav Sehgal Over a year ago

For good design, keep is_smaller() and swap() functions out of main().

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