collect string in loop and printout all the string outside loop

Question

I'm newbie here and there is some question that I want have some lesson from you guys. For example:

#include <stdio.h>
#include<stdlib.h>
#include<ctype.h>

void main()
{
    char name[51],selection;

    do
    {

    printf("Enter name: ");
    fflush(stdin);
    fgets(name,51,stdin);
    printf("Enter another name?(Y/N)");
    scanf("%c",&selection);
    selection=toupper(selection);
    }while (selection=='Y');
                     //I want to printout the entered name here but dunno the coding
printf("END\n");
system("pause");
}

As I know when the loops perform will overwrite the variable then how I perform a coding that will printout all the name user entered? I have already ask my tutor and he is ask me to use pointer, can anyone guide me in this case?

Answer 1

You've basically got two options, create a list of all the names, looping through each of them at the end, or concatenate all the names into a string as you read them, and print that whole buffer at the end. The first goes roughly like this:

 char ch[2]="Y", names[100][52]; //store up to 100 50-char names (leaving space for \n and \0)
 int x, nnames=0;
 while(nnames<100 && *ch=='Y'){
     fgets(names[nnames++], sizeof names[0], stdin); //since names is a 2d array, look
     //only at the length of a row, (in this case, names[0])
     fgets(ch, 2, stdin);
     *ch = toupper(*ch);
 }
 for(x=0; x<nnames; x++)
     //print names[x].

And the second goes roughly like this:

 char names[100*52], *np=names, *ep=names+sizeof names; //an array, the position, and the end
 char ch[2]="Y";
 while(np<ep && *ch=='Y'){
      fgets(np, ep-np, stdin); //read a name, and a newline into the buffer
      //note how I use the difference between the end and the position to tell
      //fgets the most it can possibly read
      np+=strlen(np); //advance the position to the end of what we read.
      //same deal with the y/n stuff...
 }
 printf("%s", names);

Notice the lack of loop at the end, because the whole string is stored in names.

Answer 2

You can use a linked list to store all the entered names. All data structure books talk about linked list a lot.

#include <stdio.h>
#include <stdlib.h>

struct name_node
{
    char name[100];
    struct name_node *next;
};

struct name_node* add_name(struct name_node *first, const char *name)
{
    struct name_node *p;

    /* create our node */
    p = (struct name_node*)malloc(sizeof(struct name_node));
    strcpy(p->name, name);
    p->next = NULL;

    /* link our node to the tail */
    if (first) {
        for (; first->next; first = first->next);
        first->next = p;
    }

    return p;
}

void print_names(struct name_node *first)
{
    /* print names stored in the list */
    for (; first; first = first->next) {
        printf("%s\n", first->name);
    }
}

/* free the memory we used */
void destroy_list(struct name_node *first)
{
    if (first) {
        if (first->next)
            destroy_list(first->next);

        free(first);
    }
}

int main(void)
{
    struct name_node *head = NULL;
    struct name_node *node;
    char name[100];
    char selection;

    do {
        printf("Enter name: ");
        fflush(stdin);
        fgets(name, 51, stdin);

        /* save the user input to a linked list */
        /* save head if we don't have head */
        node = add_name(head, name);
        if (!head)
            head = node;

        printf("Enter another name?(Y/N)");
        scanf("%c", &selection);
        selection = toupper(selection);
    }
    while (selection == 'Y');

    /* print the list if we have any data */
    if (head)
        print_names(head);

    /* free the memory we used */
    destroy_list(head);

    printf("END\n");
    system("pause");

    return 0;
}

Answer 3

Use a single string to get all names:

char allnames[1000] = "";

do {
    //get name in fgets
    selection = toupper(selection);
    strcat(allnames, selection);

    //Check for repetion

} while (/*there is repetion*/);

printf("%s", allnames);

You've to select the size of allnames suitably to store all names.