二叉树的C ++析构函数

Question

When i run the destructor i get a run failed and i am not sure why here is my tree header

class ExpressionTree {
private:
    ExpressionNode* root;
public:
    ExpressionTree() :
    hashmap(100000),
    root(NULL) {
    };
    virtual ~ExpressionTree(){
        helper(root);
    }

    void helper(ExpressionNode *node) {
        if ( !node ) {
            return;
        } else {
            helper( node->getLeft( ) );
            helper( node->getRight( ) );
            delete node;
        }
    }
};

and my node header

class ExpressionNode {
private:
    ExpressionNode* left;
    ExpressionNode* right;
    string data;
public:
    virtual ~ExpressionNode(){
        delete left;
        delete right;
    }
};

Now everything works fine if in the ExpressionTree class i only destroy the root but i believe i am leaking memory that way. Is that in fact the right way or is there something wrong with my recursive destruction.

Answer 1

The ExpressionNode destructor adequately cleans up it's memory which because it destroys it's children which adequately clean up their memory and so on. What you are doing right now is double-freeing the nodes; once by helper() and once by the destructors themselves. All you need to do is destroy the root node

virtual ~ExpressionTree(){
    delete root;
}

all the children nodes will be deleted through the destructors.