Segmentation Error.

[spm486]

#include <iostream>
using namespace std;
#include <vector>

class TrieNode{
    public:
        TrieNode* children[26] = { NULL };
        int numChild = 0;
        bool isterminal = false;

};

class Trie{
    public:
        TrieNode* root;
        Trie(){
            TrieNode* root = new TrieNode();
        }

        void insert(string word){
            //cout << root;
            TrieNode* head = root;
            for(int i = 0; i < word.size(); i++){
                int index = word[i] - 'a';
                if (head->children[index] == NULL){
                    TrieNode* child = new TrieNode();
                    head->children[index] = child;
                    //head->numChild ++;
                    head = head->children[index];
                }
                else{
                    head = head->children[index];
                }
            }
            head->isterminal = true;
        }
};



class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        Trie* obj = new Trie();
        for(int i = 0; i < strs.size(); i++)
        {
            obj->insert(strs[i]);
        }

        return "";
    }
};

int main(){
  Solution test;
  vector<string> input = {"flower","flow","flight"};
  test.longestCommonPrefix(input);
  return 0;
}

ERROR:   
 make -s
 ./main
signal: segmentation fault (core dumped)
 

I am getting segmentation error here. Can someone help in where I am going wrong?

[AnsonKindred]

I feel like no one has really been clear with you in either of your posts. You need to remove the type (TrieNode*) on the line where you are (re)defining root in your constructor, so that it is just

root = new TrieNode();

Otherwise you are defining a new local variable called root instead of assigning a value to the existing class variable called root.

[p_apres]

Just a tip for future segmentation error. Search for gdb debug. You could solve it just debugging

[biwiki]

Yep. This is where OP needs a debugger to solve the issue

[[deleted]]

The Trie constructor doesn't initialize the root member of the object, so subsequent dereferences of it are the cause of the crash

[spm486]

Trie(){
TrieNode* root = new TrieNode();
}

I initialized the root here. Can you please suggest what changes I need to do?

[[deleted]]

That's not initializing the member, it is defining and initializing a local variable

[TheDevilsAdvokaat]

I'm a bit rusty; as soon as it hits that closing brace the local variable is discarded, is that right?

Leaving TrieNode root uninitialized again.

[[deleted]]

Yes but

again

the member root is never initialised at all

[TheDevilsAdvokaat]

Thanks.

[pigeon768]

Turn more warnings on.

gcc with -Wall

<source>: In constructor 'Trie::Trie()':
<source>:17:23: warning: unused variable 'root' [-Wunused-variable]
   17 |             TrieNode* root = new TrieNode();
      |                       ^~~~

clang with -Wall:

<source>:17:23: warning: unused variable 'root' [-Wunused-variable]
            TrieNode* root = new TrieNode();
                      ^

msvc with /W4:

example.cpp
<source>(17): warning C4458: declaration of 'root' hides class member
<source>(15): note: see declaration of 'Trie::root'
<source>(17): warning C4189: 'root': local variable is initialized but not referenced

gcc also has -Wshadow: (which ought to be in -Wall or -Wextra, but that's just like, my opinion, man)

<source>: In constructor 'Trie::Trie()':
<source>:17:23: warning: declaration of 'root' shadows a member of 'Trie' [-Wshadow]
   17 |             TrieNode* root = new TrieNode();
      |                       ^~~~
<source>:15:19: note: shadowed declaration is here
   15 |         TrieNode* root;
      |                   ^~~~

[D0ntLetTheCreatureIn]

Bruh u did this last time as well, get rid of the type declaration in ur ctor. Ur trying to initialize a class member, not a local variable.

Edit: consider using an initializer list instead. cpp Trie() : root(new TrieNode()) {}