meow123 0 Newbie Poster

Hello, I am currently working on a binary search tree that acts as a phone book. I am nearly completed with it and all functions seem to work properly except in two cases:

An error message will not print to the screen when trying to delete or edit for a node that does not exist.

And if a node has a left and right branch, it can't be deleted.

I've been trying to fix these problems, and I was hoping that you fine folk could assist me. If you feel uncomfortable with direct answers, just giving a nudge in the right direction would be great.

Here is my code.

#include <stdio.h> 
#include <string.h> 
#include <stdlib.h>  
 /*Create phone book entry structure.*/
typedef struct pbentry {   
              char lastname[16];  
              char firstname[11]; 
              char phone[11];  
              char email[26]; } 
                Entry;
/*Create tree node structure.*/
struct tree_node {    
        Entry data;     
struct tree_node *left;     
struct tree_node *right; };   

/*Necessary functions.*/
struct tree_node * insert(struct tree_node *p, Entry e); 
struct tree_node * create_node (struct tree_node *q, struct tree_node *r, Entry e); 
struct tree_node * delete_node (struct tree_node *p, char l[], char f[]); 
struct tree_node * findmin(struct tree_node *p); 
struct tree_node * edit_node (struct tree_node *p, char l[], char f[]); 
void search_node(struct tree_node *p, char l[], char f[]); 
void print_tree(struct tree_node *p);   


int main(void) {  
       int option = 0; /*Variable for option selection.*/    
       Entry e;  /*Basic phone book entry*/    
       struct tree_node *p = NULL; /*Basic tree node*/    
       char ln[16]; /*Used for deletions, editing, and searching*/    
       char fn[11]; /*Used for deletions, editing, and searching*/      
       /*Return to menu after each instruction until the user quits.*/    
       while (option != 6) {         /*Show user the option menu.*/        
       printf("MENU\n");         
       printf("1. Add\n");         
       printf("2. Delete\n");         
       printf("3. Edit\n");         
       printf("4. Search\n");         
       printf("5. List\n");         
       printf("6. Quit\n");         
       /*Get option from the user.*/        
       printf("\nPlease select an option: ");         
       scanf("%d", &option);         

       /*If option is 1 (Add):*/    
       if (option == 1) {            
                   /*Take in subject data from the user.*/            
       printf("Please enter the last name: ");             
       scanf("%s", &e.lastname);             
       printf("Please enter the first name: ");             
       scanf("%s", &e.firstname);             
       printf("Please enter the phone number: ");             
       scanf("%s", &e.phone);             
       printf("Please enter the e-mail address: ");             
       scanf("%s", &e.email);             
       /*Create a new node.*/            
       p = insert(p, e);            
        /*Confirm node creation.*/            
        printf("Record added successfully.\n\n");    
             }        
              /*If option is 2 (Delete):*/                
       else if (option == 2) {           
              /*Take in subject data from the user.*/         

          printf("Please enter the last name: ");            
          scanf("%s", &ln);             
          printf("Please enter the first name: ");             
          scanf("%s", &fn);            
           /*Delete a node.*/            

          p = delete_node(p, ln, fn);      
             }         
             /*If option is 3 (Edit):*/            
               else if (option == 3) {            
                     /*Take in subject data from the user.*/           
          printf("Please enter the last name: ");            
          scanf("%s", &ln);            
          printf("Please enter the first name: ");            
          scanf("%s", &fn);            
           /*Edit a node.*/            
           p = edit_node(p, ln, fn);       
             }        
              /*If option is 4 (Search):*/                
          else if (option == 4) {          
            /*Take in subject data from the user.*/           
           printf("Please enter the last name: ");            

           scanf("%s", &ln);            
           printf("Please enter the first name: ");           
           scanf("%s", &fn);            
            /*Search for a node.*/            
           search_node(p, ln, fn);         
           }        
            /*If option is 5 (List):*/              
           else if (option == 5) {          
                   print_tree(p);       
                     }       
             /*If option is 6 (Quit):*/              
             else if (option == 6) {           
                 /*End the program.*/         
                    break;       
                    }        
              /*If the user does not select an existing option.*/            
              else {            
                    /*Print error message.*/            
             printf("That option does not exist. Please try again.\n\n");       
               }     
                 }    
                  return 0; }  
                /*Adds a node to the tree.*/
       struct tree_node * insert(struct tree_node *p, Entry e) 
       {     
             /*If there is no root:*/ 
            if (p == NULL) {       
             /*Create a root.*/       
              p = create_node(NULL, NULL, e);    
               }   
                 /*If there is a root, and the entry belongs before the root:*/    
             else if (strcmp(e.lastname, p->data.lastname) < 0) {      
                     /*Add before root.*/       
                      p->left = insert(p->left, e);     
                      }    
             /*If there is a root, and the entry belongs after the root:*/    
             else if (strcmp(e.lastname, p->data.lastname) > 0) {    
                       /*Add after root.*/    
                       p->right = insert(p->right, e);   
                         }    
                 /*If there is a root, and the lastnames are identical: */ 
                 else {    
                           /*If entry belongs before root: */       
                   if (strcmp(e.firstname, p->data.firstname) < 0) {          
              /*Add before root.*/          
                p->left = insert(p->left, e);        
                 }        
            /*If entry belongs after root: */    
               else if (strcmp(e.firstname, p->data.firstname) > 0) {    
                   /*Add after root.*/      
                p->right = insert(p->right, e);   

                     }        
                /*If entries are the same: */     
            else {           


                  /*Do nothing.*/       
                     return p;       
                       }    
                        }   
                 /*Return revised tree.*/ 
                    return p; 
                    }   
/*Creates a new node.*/
struct tree_node * create_node (struct tree_node *q, struct tree_node *r, Entry e) {     
       struct tree_node* newnode;     
       newnode = (struct tree_node*)(malloc(sizeof(struct tree_node)));     
       newnode->data = e;     
       newnode->left = q;     
       newnode->right = r;     
       return newnode; }  

 /*Deletes a node from the tree.*/
 struct tree_node * delete_node (struct tree_node *p, char l[], char f[]) {   

          if (p == NULL) {     return NULL; } 
/*If entry is before root:*/   
           if (strcmp(l, p->data.lastname) < 0 || strcmp(f, p->data.firstname) != 0) 
           {        
 /*Delete from before root.*/       
  p->left = delete_node(p->left, l, f);    
   }     
  /*If entry is after root:*/   
   else if (strcmp(l, p->data.lastname) > 0 || strcmp(f, p->data.firstname) != 0) {  

  /*Delete from after root.*/       
   p->right = delete_node(p->right, l, f);    
    }    
    /*If entry is located and has a left and right branch:*/ 
       else if (p->left != NULL && p->right != NULL) {   

       /*Find which branch moves up in the tree.*/  
       p->data = findmin(p->right)->data;        
       p->right = delete_node(p->right, l, f);        
        /*Confirm node deletion.*/        
        printf("Record deleted successfully.\n\n");     
        }     
        /*If entry is located and has a left branch:*/    
        else if (p->left != NULL) {         
             /*Move left branch up.*/       
              p = p->left;         
              /*Confirm node deletion.*/        
              printf("Record deleted successfully.\n\n");   
                }   
                  /*If entry is located and has a right branch:*/  
                    else if (p->right != NULL) {      
                            /*Move right branch up.*/       
                     p = p->right;      
                                /*Confirm node deletion.*/  
                   printf("Record deleted successfully.\n\n");    
                    }    
                     /*If entry is not found:*/ 
                else {       
                   /*Error.*/     
                  printf("Record could not be found.\n\n");    

                   }     
                   /*Return revised tree.*/    
                   return p; }   
 /*Finds the leftmost node in the right branch.*/
 struct tree_node * findmin(struct tree_node *p) {    
         /*If left node is not empty.*/    
         if (p->left != NULL) {         
                     /*Go to the left node.*/        
         findmin(p->left);     }     
         /*Return leftmost node.*/    
         return p; }   
         /*Edits a node's data.*/

         struct tree_node * edit_node (struct tree_node *p, char l[], char f[]) {  

         char num[11]; 
         /*Used to determine course of action.*/    
         char e[26]; 
         /*Used to determine course of action.*/   
          /*If entry is before root:*/   
          if (p == NULL) {     return NULL; } 

           if (strcmp(l, p->data.lastname) < 0) {         
                         /*Check before root.*/        
           edit_node(p->left, l, f);     }    
            /*If entry is after root:*/   
            else if (strcmp(l, p->data.lastname) > 0) {       
               /*Check after root.*/        
            edit_node(p->right, l, f);     
            }   
              /*If last name is found and first names are different:*/   
               else if (strcmp(l, p->data.lastname) == 0 && strcmp(f, p->data.firstname) != 0) {         
               /*If entry is before root.*/        
               if (strcmp(f, p->data.firstname) < 0) { 

    /*Check before root.*/            
    edit_node(p->left, l, f);        
     }         
     /*If entry is after root.*/        
     if (strcmp(f, p->data.firstname) > 0) {             
                   /*Check after root.*/            
                   edit_node(p->right, l, f);         
                   }    
                    }    
    /*If entry is located:*/   
     else if (strcmp(l, p->data.lastname) == 0 && strcmp(f, p->data.firstname) == 0) { 

              /*Ask for new phone number and retreive.*/        
          printf("New phone number (Enter s to skip): ");         
          scanf("%s", &num);        
           /*If skipped:*/        
           if (strcmp(num, "s") == 0) {             
           /*Ask for new email address and retreive.*/            
           printf("New email address (Enter s to skip): ");             
           scanf("%s", &e);            
            /*If skipped:*/           
            if (strcmp(e, "s") == 0) {
                   /*Confirm node edit.*/                
                   printf("Record edited successfully.\n\n");                 
     /*Return revised tree.*/                
     return p;             
     }             
     /*If email address is to be changed:*/            
     else {                 
          /*Change email*/               
         strcpy(p->data.email, e);                 
         /*Confirm node edit.*/                
         printf("Record edited successfully.\n\n");           
           }     
               }     
                   /*If phone number is to be changed:*/        
           else {             
                /*Change phone number.*/            
                strcpy(p->data.phone, num);             
           /*Ask for new email address and retreive.*/            
           printf("New email address (Enter s to skip): ");             
           scanf("%s", &e);            
           /*If skipped:*/            
           if (strcmp(e, "s") == 0) {                
                          /*Confirm node edit.*/               
            printf("Record edited successfully.\n\n");                
             /*Return revised tree.*/                
             return p;            
              }           
                /*If email address is to be changed:*/            
                else {               
                       /*Change email.*/              
                         strcpy(p->data.email, e);    
                /*Confirm node edit.*/                
                printf("Record edited successfully.\n\n");           
                 }  
                        }  
                           }     
    /*If entry is not found:*/    
    else {        
          /*Error.*/        
          printf("Record could not be found.\n\n");     
          }    
           /*Return revised tree.*/    
           return p; }  
            /*Searches for a node and retrieves data.*/
 void search_node(struct tree_node *p, char l[], char f[]) {    
       /*If entry is before root:*/    
         if (p == NULL) {     printf("Member not found.\n");     return; }
       if (strcmp(l, p->data.lastname) < 0) {         
                     /*Check before root.*/
               search_node(p->left, l, f);     
               }     
       /*If entry is after root:*/    
       else if (strcmp(l, p->data.lastname) > 0) {
       /*Check after root.*/       
        search_node(p->right, l, f);    
         }    
          /*If last name is found and first names are different:*/  
            else if (strcmp(l, p->data.lastname) == 0 && strcmp(f, p->data.firstname) != 0) {  
           /*If entry is before root.*/        
           if (strcmp(f, p->data.firstname) < 0) {             
                         /*Check before root.*/           
                          search_node(p->left, l, f);     
                          }        
           /*If entry is after root.*/       
          if (strcmp(f, p->data.firstname) > 0) {           
                    /*Check after root.*/           
                 search_node(p->right, l, f);        
                  }   
                   }     
 /*If entry is located:*/    
 else if (strcmp(l, p->data.lastname) == 0 && strcmp(f, p->data.firstname) == 0) {  
        /*Print out data.*/       
         printf("%s, %s, %s, %s\n\n", p->data.lastname, p->data.firstname, p->data.phone, p->data.email);        
          }     
          /*If entry is not found:*/   
           else {      
                   /*Error.*/       
                    printf("Record could not be found.\n\n");    
                     } 
                     }  
             /*Prints contents of tree.*/
             void print_tree(struct tree_node *p) {   
             /*if tree has nodes:*/    
             if (p != NULL) {         
                   /*Print node data.*/        
                   print_tree(p->left);        
                   printf("%s, %s, %s, %s\n\n", p->data.lastname, p->data.firstname, p->data.phone, p->data.email);        
                    print_tree(p->right);     }



                     }
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