I am using C, and I am using putty when I make codes and run it. I have the code
ID: 3859001 • Letter: I
Question
I am using C, and I am using putty when I make codes and run it.
I have the code below, and it keeps giving me seg fault.
Please tell me what's wrong!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXCITYNAME 30
#define MAXLINELENGTH 50
typedef struct n_
{
int zipCode;
char* city;
char state[3]; //A state abbreviation. Note that we need
//room for the NULL terminator!
struct n_* left; //connections to other nodes
struct n_* right;
} Node;
Node* importTree(char* filename);
Node* addNode(Node* root, Node* newNode);
int findStateCount(Node* root, char* state);
Node* findZipCode(Node* root, int zipCode);
void freeTree(Node* root);
int main(int argc, char** argv)
{
// checking for proper arguments
if(argc != 2) {
printf("Usage: %s <filename> ", argv[0]);
exit(1);
}
// maintain the root of the tree
Node* root = NULL;
// read da file, make da tree
root = importTree(argv[1]);
if(root == NULL) {
printf(" Failed to import tree from file");
exit(1);
}
int results = 0;
int input = 0;
int zipSearch = 0;
Node* zipNode = NULL;
char* stateSearch = malloc(sizeof(char)*3);
// menu operation
while(1) {
printf(" 1: find number in a state");
printf(" 2: find a ZIP code");
printf(" 3: exit");
printf(" > ");
scanf("%d", &input);
switch(input) {
case 1:
printf(" Enter the state you want to search for:");
printf(" > ");
scanf("%s", stateSearch);
// find number of results per state
results = findStateCount(root, stateSearch);
if(results == 0) {
printf(" No results found for that state code");
} else {
printf(" The state has %d results in the sample", results);
}
break;
case 2:
// search for a ZIP code
printf(" Enter the ZIP you want to find:");
printf(" > ");
scanf("%d", &zipSearch);
// TODO: check the zipcode entered is 5 digits
zipNode = findZipCode(root, zipSearch);
if(zipNode == NULL) {
printf(" No results found for %d", zipSearch);
} else {
printf(" Result found for %d: ", zipSearch);
printf(" City: %s", zipNode->city);
printf(" State: %s", zipNode->state);
}
break;
case 3:
// quit
freeTree(root);
free(stateSearch);
exit(0);
break;
default:
printf(" Invalid selection, choose again: ");
}
}
// just in case we break out of our switch statement, make sure everything is free
freeTree(root);
free(stateSearch);
return 0;
}
Node* addNode(Node* root, Node* newNode)
{
// the new node shouldnt be null
if(newNode == NULL) {
printf(" NULL pointer passed to addNode()");
exit(1);
}
// if there is no tree, newnode starts the tree
if(root == NULL) {
return newNode;
} else {
// big zip codes on the right
// big zip codes on the right
if(newNode->zipCode > root->zipCode) {
root->right = addNode(root->right, newNode);
}
// lil zip codes on the left
if(newNode->zipCode < root->zipCode) {
root->left = addNode(root->left, newNode);
}
}
return root;
}
int findStateCount(Node* root, char* state)
{
// if the tree is empty, theres no instances of the state
if(root == NULL) {
return 0;
} else {
// this part increments our return if the state match
// strcmp returns 0 if matching
if(strcmp(root->state, state) == 0) {
return 1 + findStateCount(root->left, state) + findStateCount(root->right, state);
}
// traverse down the sides of the tree
return findStateCount(root->left, state) + findStateCount(root->right, state);
}
Node* findZipCode(Node* root, int zip)
{
if(root == NULL) {
return NULL;
} else {
if(root->zipCode == zip) {
return root;
}
Node* x = NULL;
}
// test the left side
x = findZipCode(root->left, zip);
if(x != NULL) {
return x;
}
// test the right side
x = findZipCode(root->right, zip);
if(x != NULL) {
return x;
}
}
// if nothing is found
return NULL;
}
void freeTree(Node* root)
{
if(root == NULL) {
return;
}
freeTree(root->left);
freeTree(root->right);
// make sure to account for the city pointer
free(root->city);
free(root);
}
Node* importTree(char* filename)
{
// we always want to maintain the root of the tree
Node* root = NULL;
// open up the text file
FILE* fp = fopen(filename, "r");
// if opening the file fails, break
if(!fp)
{
printf("Error opening file. ");
return NULL;
}
// this loop continues until the file pointer reaches the EOF
while(!feof(fp))
{
// creat a new node pointer, one for each iteration of the loop
Node* new = malloc(sizeof(Node));
// if the memory allocation fails, something went wrong or we're out of memory
if(!new)
{
printf("Failed to allocate memory. Ending read. ");
exit(1);
}
// the city field inside the node struct is a pointer, so allocate memory
// for that field
new->city = malloc(sizeof(char)*MAXCITYNAME);
// again, if memory allocation fails, something went wrong or we're out
if(!(new->city))
{
printf("Failed to allocate memory. Ending read. ");
exit(1);
}
// set both children pointers of the new node to NULL (beacuse we haven't
// read new children for this node yet. addNode() does that later
new->left = NULL;
new->right = NULL;
// this is the 'buffer' that we're scanning the file into.
char* line = malloc(sizeof(char)*MAXLINELENGTH);
// guess what...if we can't malloc memory for the buffer, something is wrong
if(!line)
{
printf("Failed to allocate memory. Ending read. ");
exit(1);
}
// if fgets() encounters an error, it returns null. this will occur at the
// end of the file as well, but the next if statement accounts for that.
if(fgets(line, MAXLINELENGTH, fp) == NULL)
{
// if fgets() returns null and it's not the end of the file, somethings
// went wrong.
if(!feof(fp))
{
printf("File reading ended prematurely. Check for errors in file. ");
exit(1);
}
// either way, if fgets() fails (or we're at EOF), we don't have
// anything to put in the pointers that we just allocated memory for,
// so we need to free that up
free(new->city);
free(line);
free(new);
// close up our file.
fclose(fp);
break;
}
// temporary pointer will store the tokens that strtok finds.
char* tmp = strtok(line, ",");
// atoi convertts our char* to an integer which we can put in the node
new->zipCode = atoi(tmp);
// by calling strtok() with a NULL pointer, we advance to the next
// token string
tmp = strtok(NULL, ",");
// we don't use assignment operators with strings, we use strcpy() to copy
// into the memory
strcpy(new->city, tmp);
// since we're dealing with tokens, we need to append NULL terminator
// characters to the city and state fields
new->city[strlen(tmp)+1] = '';
// advancing to the next token: the state field
// the same process follows for the city field as for the state field for the
// next 3 lines
tmp = strtok(NULL, ",");
strcpy(new->state, tmp);
new->state[2] = '';
// finally, once the node has been filled with the parsed info,
// call addNode and stick it in our tree.
root = addNode(root, new);
// if the addNode() calls fail, root will still be NULL, and that's not right.
if(!root)
{
printf("Root of tree is still NULL! Ending read. ");
exit(1);
}
// free up memory from our buffer
free(line);
}
// once we've read the file and built the tree, return it.
return root;
}
Explanation / Answer
Ans:: There is a minor error in the code.
1:: In the findZip x is used but not declared.
2:: return makes integer from pointer without a cast ( return NULL ) .
3:: There is undefined reference to findZipCode in main.
Thank you.
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