Issue with array of pointers

Question

I'm writing a program to alphabetize inputted names and ages. The ages are inputted separately, so I know I need to use an array of pointers to tie the ages to the array of names but I can't quite figure out how to go about doing it. Any ideas?

So far, my program only alphabetizes the names.

/* program to alphabetize a list of inputted names and ages */

#include <stdio.h>
#define MAXPEOPLE 50
#define STRSIZE 

int alpha_first(char *list[], int min_sub, int max_sub);
void sort_str(char *list[], int n);

int main(void)
{
    char people[MAXPEOPLE][STRSIZE];
    char *alpha[MAXPEOPLE];
    int num_people, i;
    char one_char;

    printf("Enter number of people (0...%d)\n> ", MAXPEOPLE);
    scanf("%d", &num_people);

    do
        scanf("%c", &one_char);
    while (one_char != '\n');

    printf("Enter name %d (lastname, firstname): ", );
    printf("Enter age %d: ", );
    for (i = 0; i < num_people; ++i)
        gets(people[i]);

    for (i = 0; i < num_people; ++i)
        alpha[i] = people[i];
    sort_str(alpha, num_people);

    printf("\n\n%-30s5c%-30s\n\n", "Original List", ' ', "Alphabetized List");

    for (i = 0; i < num_people; ++i)
        printf("-30s%5c%-30s\n", people[i], ' ', alpha[i]);

    return(0);
}

int alpha_first(char *list[], int min_sub, int max_sub)
{
    int first, i;

    first = min_sub;
    for (i = min_sub + 1; i <= max_sub; ++i)
        if (strcmp(list[i], list[first]) < 0)
            first = i;

    return (first);
}

void sort_str(char *list[], int n)
{
    int fill, index_of_min;
    char *temp;

    for (fill = 0; fill < n - 1; ++fill){
        index_of_min = alpha_first(list, fill, n - 1);

        if(index_of_min != fill){
            temp = list[index_of_min];
            list[index_of_min] = list[fill];
            list[fill] = temp;
        }
    }
}

Hey, this is a lot of code, is there any pieces of this that can be omitted? I'm much more willing to help when I don't have to try to read 50 lines of uncommented C. — daniel gratzer
– daniel gratzer, Commented Jul 17, 2013 at 19:44
Have you learned about structures yet? If so, you should probably using them. — Jonathan Leffler
– Jonathan Leffler, Commented Jul 17, 2013 at 19:50
The other (poorer) alternative to structs is to just sort your list of ages at the same time, and in the same way, that you sort your list of names. Please learn how to indent your code, too. — Crowman
– Crowman, Commented Jul 17, 2013 at 19:51

Jens · Accepted Answer · 2013-07-17 21:26:05Z

1

Most of your printfs are syntax errors, as in

printf("Enter name %d (lastname, firstname): ", );
printf("Enter age %d: ", );

or bomb right away, since you pass an int (' ') as a pointer:

printf("\n\n%-30s5c%-30s\n\n", "Original List", ' ', "Alphabetized List");

As a first step, get all your %s right and show us what you really compiled, not some random garbage. And crank your compiler's warning level to the maximum, you need it! What is

#define STRSIZE

supposed to mean when STRSIZE is used as an arary dimension? You have a serious cut&paste problem, it would appear.

edited Jul 17, 2013 at 21:26

answered Jul 17, 2013 at 21:10

Jens

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Comments

aiguofer · Accepted Answer · 2013-07-17 20:09:10Z

0

Creating a struct would probably be easier: i.e

struct person {
   char name[STRSIZE];
   int age;
}

Otherwise, if you must do it the way you're trying, just create an extra array of the indexes. When you move a name, you also move the index on the array... when you're done sorting names, just sort the ages to match the indexes.

answered Jul 17, 2013 at 20:09

aiguofer

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