Question

I am getting above error , if anybody have any idea please help me.

I am getting this error in void traverse function where i have used insert function for inserting into map.

struct node {
    int weight;
    unsigned char value;
    const node *child0;
    const node *child1;
    map<unsigned char, string> huffmanTable;

    node( unsigned char c = 0, int i = -1 ) {
        value = c;
        weight = i;
        child0 = 0;
        child1 = 0;
    }

    node( const node* c0, const node *c1 ) {
        value = 0;
        weight = c0->weight + c1->weight;
        child0 = c0;
        child1 = c1;
    }

    bool operator<( const node &a ) const {
        return weight >a.weight;
    }

    void traverse(ostream& o,string code="") const {

    if ( child0 ) {
        child0->traverse(o, code + '0' );
        child1->traverse(o, code + '1' );
    } else {
        o<<value<<"\t";
        cout <<" " <<value <<"    ";

        o<<weight<<"\t";
        cout <<weight;
        o<<code<<endl;

        cout <<"     " <<code <<endl;
        huffmanTable.insert(pair<unsigned char, std::string>(value,code));

    }
}

};

Answer 1

You are trying to add to the map huffmanTable from a const function. A const member function is not allowed to modify the this object. Your options are

1. You can make the map mutable

   mutable map huffmanTable;

or

1. Remove the const from traverse function

   void traverse(ostream& o,string code=””){