diff tree4/tree.c tree5/tree.c
3c3
<  *  (version 4: separating the 'tree' struct from the 'treenode' struct)
---
>  *  (version 5: keyed by a string instead of int)
9a10
> #include <string.h>
16c17
<   int key;		           // search key for this item
---
>   char *key;		           // search key for this item
33,35c34,36
< 				      const int key, void *data);
< static treenode_t *treenode_new(const int key, void *data);
< static void *tree_find_helper(treenode_t *node, const int key);
---
> 				      const char *key, void *data);
> static treenode_t *treenode_new(const char *key, void *data);
> static void *tree_find_helper(treenode_t *node, const char *key);
54c55
< tree_insert(tree_t *tree, const int key, void *data)
---
> tree_insert(tree_t *tree, const char *key, void *data)
67c68
< tree_insert_helper(treenode_t *node, const int key, void *data)
---
> tree_insert_helper(treenode_t *node, const char *key, void *data)
72c73
<   } else if (key == node->key) {
---
>   } else if (strcmp(key, node->key) == 0) {
79c80
<     if (key < node->key) {
---
>     if (strcmp(key, node->key) < 0) {
91c92
< treenode_new(const int key, void *data)
---
> treenode_new(const char *key, void *data)
95a97
>     // error allocating memory for node; return error
98,102c100,112
<     node->key = key;
<     node->data = data;
<     node->left = NULL;
<     node->right = NULL;
<     return node;
---
>     node->key = malloc(strlen(key)+1);
>     if (node->key == NULL) {
>       // error allocating memory for key; 
>       // cleanup and return error
>       free(node);
>       return NULL;
>     } else {
>       strcpy(node->key, key);
>       node->data = data;
>       node->left = NULL;
>       node->right = NULL;
>       return node;
>     }
108c118
< tree_find(tree_t *tree, const int key)
---
> tree_find(tree_t *tree, const char *key)
122c132
< tree_find_helper(treenode_t *node, const int key)
---
> tree_find_helper(treenode_t *node, const char *key)
126c136
<   } else if (key == node->key) {
---
>   } else if (strcmp(key, node->key) == 0) {
129c139
<     if (key < node->key) {
---
>     if (strcmp(key, node->key) < 0) {
diff tree4/tree.h tree5/tree.h
3c3
<  *  (version 4: separate tree from treenode)
---
>  *  (version 5: keyed by a string instead of int)
22a23
>  * The key string is copied for use by the tree.
24c25
< void tree_insert(tree_t *tree, const int key, void *data);
---
> void tree_insert(tree_t *tree, const char *key, void *data);
29c30
< void *tree_find(tree_t *tree, const int key);
---
> void *tree_find(tree_t *tree, const char *key);
diff tree4/treetest.c tree5/treetest.c
4c4
<  * 
---
>  *
17a18,21
>   if (tree == NULL) {
>     printf("tree_new failed\n");
>     exit(1);
>   }
20,28c24,32
<   tree_insert(tree, 3, datastring);
<   tree_insert(tree, 4, datastring);
<   tree_insert(tree, 1, datastring);
<   tree_insert(tree, 5, datastring);
<   tree_insert(tree, 6, datastring);
<   tree_insert(tree, 2, datastring);
<   tree_insert(tree, 8, datastring);
<   tree_insert(tree, 7, datastring);
<   tree_insert(tree, 0, datastring);
---
>   tree_insert(tree, "alice", datastring);
>   tree_insert(tree, "charlene", datastring);
>   tree_insert(tree, "hillary", datastring);
>   tree_insert(tree, "irina", datastring);
>   tree_insert(tree, "eve", datastring);
>   tree_insert(tree, "bob", datastring);
>   tree_insert(tree, "david", datastring);
>   tree_insert(tree, "fred", datastring);
>   tree_insert(tree, "george", datastring);
31,32c35,36
<   printf("find %d returns %s\n", 4, tree_find(tree, 4));
<   printf("find %d returns %s\n", 5, tree_find(tree, 5));
---
>   printf("find %s returns %s\n", "irina", tree_find(tree, "irina"));
>   printf("find %s returns %s\n", "eve", tree_find(tree, "eve"));
34,37c38,41
<   printf("update node %d...\n", 5);
<   tree_insert(tree, 5, "new string");
<   printf("find %d returns %s\n", 5, tree_find(tree, 5));
<   printf("find null returns %s\n", tree_find(NULL, 5));
---
>   printf("update node %s...\n", "eve");
>   tree_insert(tree, "eve", "new string");
>   printf("find %s returns %s\n", "eve", tree_find(tree, "eve"));
>   printf("find null returns %s\n", tree_find(NULL, "eve"));