names and numbers in binary trees

i am trying to create a list of phone numbers and names that has the following input:
name number
name number
name number
.

what i need is for a person to enter data in that format and terminate input by pressing '.' on a newline. after that a program should ask a user to enter a name and in return display a number.
i have created such program but i am stuck on how to make it display number for a given name. currently when user inputs a name it returns a name. How do i make it return a number?
thanks

A hashmap would be good for this.

Quote:

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Originally Posted by mike_g

A hashmap would be good for this.

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As long as you don't need to also print a sorted list on name - as a hashed list will not be in alphabetical order.

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Mats

i am a beginner in C so i haven't covered hash tables yet...
here is what i wrote so far

Code:

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

typedef struct tree { char thisnode[10]; struct tree *left; struct tree *right;} Tree;

Tree *makenode (char *in, Tree *l, Tree *r)
{
        Tree *t = malloc( sizeof(Tree));
        t -> left = l;
        t -> right = r;
        strncpy (t -> thisnode, in, 9);
        return t;
}

Tree *insert (Tree *root, char *what)
{
        if (root ==NULL){
                root = makenode (what, NULL, NULL);
                }else if (strcmp (what, root -> thisnode) < 0){
                root -> left = insert (root -> left, what);
                }else{
                root -> right = insert(root -> right, what);
                }
                return root;
}

char *search (Tree *root, char *what)
{
        if (root ==NULL){
                return "Not Found";
        }else if (strcmp(what, root -> thisnode) == 0){
        return root -> thisnode;
        }else if (strcmp(what, root -> thisnode) < 0 ) {
                return search (root -> left, what);
                }else{
                return search (root -> right, what);
                }
}

int main (void)
{
        char s[30]; Tree *tree = NULL;
        do {
        scanf( " &#37;s", s);
        if (strcmp(s, ".") != 0){
                tree = insert (tree, s);
                }
        } while (strcmp(s, ".") != 0);
        do{
        printf("Type a name please:");
        scanf(" %s",s);
        if (strcmp(s,".") != 0){
                printf("%s\n", search (tree,s ));
        }
        }while (strcmp(s, ".") != 0);
}

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So what exactly is the problem you are having with the code?

I expect that a 10 char string may be a bit short, but other than that, I don't see anything immediately wrong.

--
Mats

oops changed that. There is nothing wrong with the code as it is. The problem i am having is rooted in the fact that i know how to build trees with numbers or names; i just never built one with both. So i cant visualise the tree in my head. For example if i enter a NAME space NUMBER, i assume it creates a root with name and a branch with number, so when i enter a new NAME space NUMBER at newline it repeats the same process. But how can it compare a numeric value to alpha value and decide whether it is larger or smaller so it can place it in the left or right node? So to answer your question: at present the code prints NAME instead of the NUMBER. How do I change it so it prints NUMBER? thanks

Ok, so you need to split the "name" and "number" components, and have a "name" and "number" entry in your nodes.

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Mats

ok so you mean something like this:

scanf("%s", L);
scanf("%s", N)

would that work??

I'm not a great fan of using scanf() for input, but yes, something like that.

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Mats