Segmentation fault in trie implementation using vector c++ - c++

Question

#include <iostream>
#include <vector>
#include <string>
using namespace std;
#define LOWERCASE_ALPHABET_SiZE 26
typedef int (*ptr) (char );
inline int charToIndex(char a) { return a - 'a'; };
class trienode
{
private:
vector< trienode* > child;
bool leaf;
public:
trienode(int );
~trienode();
void initialiseChild(int i);
trienode* getChild(int i);
void setLeaf() { leaf = true; };
bool isLeaf() { return leaf; };
};
trienode::trienode(int size)
{
for(int i = 0; i < size; i++)
{
child.push_back(NULL);
}
leaf = false;
}
trienode::~trienode()
{
for(int i = 0; i < child.size(); i++)
{
delete child.at(i);
child.at(i) = NULL;
}
}
void trienode::initialiseChild(int i)
{
child.at(i) = new trienode(child.size());
}
trienode* trienode::getChild(int i)
{
return child.at(i);
}
class trie
{
private:
trienode* root;
ptr toIndex;
public:
trie(int , ptr );
~trie();
void insert(const string& ref);
bool search(const string& ref);
};
trie::trie(int size, ptr toIndex) : toIndex(toIndex), root(new trienode(size)) { }
trie::~trie()
{
cout << "In destructor trie" << endl;
delete root;
root = NULL;
}
void trie::insert(const string& ref)
{
int size = ref.size();
trienode* root = root;
for(int i = 0; i < size; i++)
{
int index = toIndex(ref[i]);
if(root->getChild(index) == NULL) // crashing in getChild()
{
root->initialiseChild(index);
}
root = root->getChild(index);
}
root->setLeaf();
}
bool trie::search(const string& ref)
{
trienode* root = root;
int size = ref.size();
for(int i = 0; i < size && root != NULL; i++)
{
int index = toIndex(ref[i]);
if((root = root->getChild(index)) == NULL)
{
break;
}
}
return (root != NULL && root->isLeaf());
}
int main(int argc,char* argv[])
{
trie* altrie = new trie(LOWERCASE_ALPHABET_SiZE, charToIndex);
int n;
string temp;
cin >> n;
for(int i = 0; i < n; i++)
{
cin >> temp;
altrie->insert(temp);
}
int k;
for(int i = 0; i < k; i++)
{
cin >> temp;
if(altrie->search(temp))
{
cout << temp << " exists in the trie" << endl;
}
else
{
cout << temp << " doesn`t exist in the trie" << endl;
}
}
return 0;
}
I am creating Trie by supplying no of children it can have in each level and function pointer to convert the given character to index. After that I am Creating the root node of trie and when I`m inserting the first string it is getting Segmentation Fault in getChild Function
First things first explain me the reason behind the crash.
Explain me how I can improve the implementation of trie.

Answer 1

You are using the same name for member and local variables, like this:
trienode* root = root;
The compiler cannot tell the diffirence between the local root and trie::root so you are assigning it to itself.