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?
        // ...
    }
    // ...
}