Implementation of Trie data structure

Question

I am new at programming. I am trying to implement Trie dataStructure. But there is segmentation fault whenever i try to insert a string into trie.

Here is the Node class

class Node{
    public:
        Node *key[2];
        Node *parent;
        bool EOW;
        Node1(){
            this->key[0]=NULL;
            this->key[1]=NULL;
            this->parent = NULL;
            this->EOW = false;
        }
};

and this is the trie class

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

        void insertUtil(Node *root, char a[]);
        void insert(char a[]){
            // cout << root <<endl;
            // cout << root->key[0];
            insertUtil(root, a);
        }
};

and this is the insertUtil function

void Trie::insertUtil(Node *root, char a[]){
    Node *temp = root;
    for(int idx=0;idx<5;idx++){
        cout << idx <<endl;
        int tmp_chr = a[idx]-'0';
        if(!(temp->key[1])){
            temp->key[a[idx]-'0'] = new Node();
            temp->key[a[idx]-'0']->parent = temp;
        }
        temp = temp->key[a[idx]-'0'];
    }
    temp->EOW = -1;
}

int main(){
    Trie t1;
    char b[5];
    cin >> b;
    t1.insert(b);
    cout << '*';
    cin >> b;
    t1.insert(b);
    cin >> b;
    t1.insert(b);
    cin >> b;
    t1.insert(b);
}

Answer 1

The member key of Node is declared as

Node *key[2];

So it's an array of two pointers and given this line in Trie::insertUtil ,

int tmp_chr = a[idx]-'0';  // A variable ignored in the following code, BTW.

I'll assume that the "strings" that the OP is trying to insert are composed only by the characters '0' and '1' .

Note that, in the posted code, the null-terminator needed in the used C-string is simply ignored, which is an error by itself, easily fixed by using a proper std::string instead.

The other issue is in the same loop:

for(int idx = 0; idx < 5; idx++)
{   //           ^^^^^^^                   It should stop before the null-terminator
    // (...)
    int tmp_chr = a[idx]-'0'; //           Are you sure that there are only '0' or '1'?
    if( !(temp->key[1]) )
    { //           ^^^                     1 is wrong, here, it should be temp->key[tmp_chr]
        temp->key[a[idx]-'0'] = new Node();
        //        ^^^^^^^^^^               Why not use tmp_chr here and in the following?
        // ...
    }
    // ...
}