Hi Aditya,
In C++ member variables gets initialized to garbage values. So in
child function T->Symbol is garbage and is not null so it returns because
of null check. Next in your insert method you try to access that garbage
value. This will cause a crash.
When you remove the cmnt1, you intialize symbol field properly and hence
you see no crash.
As a general practice, always initialize member variables in C++ to some
value. I believe that was your intention of calling child method from
makeTrie function.
Regards,
Sachin
On Sun, Dec 23, 2012 at 5:48 AM, Aditya Raman <[email protected]>wrote:
> Hello everyone,
> I was trying to implement Trie in c++ for the first time and got some
> issues in coding its implementation.
> The code has 2 commented lines namely cmnt1 and cmnt 2.
> I dont understand how does it make a difference if i use cmnt1 instead of
> cmnt2 .
> Both lines are intended to check if a node in the Trie has childs never
> initialized before.
>
> ----------------------------- Code Below
> -----------------------------------------------
>
> #include <fstream>
> #include <iostream>
> #include <cstdio>
> #include <algorithm>
> #include <cstring>
> #include <string>
> #include <cctype>
> #include <stack>
> #include <queue>
> #include <list>
> #include <vector>
> #include <map>
> #include <sstream>
> #include <cmath>
> #include <bitset>
> #include <utility>
> #include <set>
> #include <numeric>
> using namespace std;
> struct TrieNode
> {
> bool leaf;
> TrieNode* symbol;
> };
>
> void child(TrieNode* T)
> {
>
> ////cmnt1////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
>
> ////////if( T->symbol != NULL)return;
>
> ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
>
> T->symbol=(TrieNode*)malloc(26*sizeof(TrieNode));
>
> for(int i=0;i<26;i++)
> { T->symbol[i].leaf=false;
> T->symbol[i].symbol=NULL;
> }
> }
>
> TrieNode* makeTrie( )
> {
> TrieNode* T=(TrieNode*)malloc(sizeof(TrieNode));
> T->leaf=false;
> child(T);
> return T;
> }
>
> void insert(string A,TrieNode* root)
> {TrieNode* temp=root;
> int i;
> for(i=0;i<A.length()-1;i++)
> { temp=&(temp->symbol[A[i]-'A']);
>
>
> //cmnt2//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
> if( temp->symbol== NULL)
>
>
> /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
> child(temp);
> }
> temp=&(temp->symbol[A[i]-'A']);
> temp->leaf=true;
> }
> vector<char> display;
> void print(TrieNode* T)
> {
> if(T->leaf==true){ for(int i=0;i<display.size();i++)cout<<display[i]<<"
> ";cout<<endl; }
> if(T==NULL)return;
> if(T->symbol!=NULL){
> for(int i=0;i<26;i++)
> {
> display.push_back('A'+i);
> print(&T->symbol[i]);
> display.pop_back(); }
> }
> }
>
> int main()
> {
> TrieNode* root=makeTrie();
> insert("ADI",root);
> insert("CAT",root);
> insert("ADII",root);
> print(root);
> // system("pause");
> }
>
> -----------------end of code---------------------
>
>
> if i remove code of cmnt 1(like in the pasted code) and directly use the
> code of cmnt 2 then trie code runs smooth .But if do the opposite case
> ,which is logically the same ,the code fails to run. kindly help!
>
> --
>
>
>
--
Regards,
Sachin Maheshwari
Cell phone: +91.7259917298
"If we admit that human life can be ruled by reason; the possibility of
life is destroyed." - Alexander Supertramp
--
