问一个二叉树的 赋值函数 实现
template <typename T> class BinaryTree;
template <typename T> class BinNode {
template <typename T> friend class BinaryTree;
public:
....
private:
T data;
BinNode <T> *leftChild;
BinNode <T> *rightChild;
};
template <typename T> class BinaryTree {
public:
BinaryTree(void) { // default constructor
this-> root = NULL;
}
BinaryTree(char endflag ) { // constructor, input level sequence
T *a = new T[treeDefaultSize];
T data;
int k = 0;
cout < < "Input char data to construct a binaryTree( '@ ' stands for NULL node).Ending with '# '. " < < endl;
cin > > data;
while (k < treeDefaultSize && data != endflag) {
a[k++] = data;
cin > > data;
}
if (k < treeDefaultSize) {
this-> root = createBinaryTree(a, 0, k);
delete []a;
a = NULL;
}
else {
delete []a;
a = NULL;
cerr < < "Node numbers exceed maxSize " < < endl;
exit(1);
}
}
BinaryTree(T data) { // constructor
this-> root = new BinNode <T> (data);
}
BinaryTree(const BinaryTree <T> & otherTree) { //copy constructor
..........
}
BinaryTree & operator = (BinaryTree <T> &otherTree) { // =
if(this != &otherTree) {
destroy(this-> root); //??????
this-> root = copyBinaryTree(otherTree.getRoot());
}
return *this;
}
BinNode <T> * createBinaryTree(T *a, int i, int n) {
if (i < n) {
BinNode <T> *p = NULL;
if (a[i] == '@ ') {
p = NULL;
}
else {
p = new BinNode <T> (a[i]);
p-> setLeftChild(createBinaryTree(a, 2 *i + 1, n));
p-> setRightChild(createBinaryTree(a, 2 * i + 2, n));
}
return p;
}
else {
return NULL;
}
}
......
private:
void destroy(BinNode <T> *p) {
if (p != NULL) {
destroy(p-> getLeftChild());
destroy(p-> getRightChild());
delete p;
}
}
BinNode <T> *root;
};
问题就出在语句 //?????? 处，我想先删除this所指的树，然后在赋值。问题是：
this所指的二叉树对象我无法让叶子的左右孩子为空，所以执行到那句就指针错误。如果注释掉，就不会有错误了，这样有memory leak。
谁给个解决办法被，谢了！
[解决办法]
给类添加默认构造函数：
template <typename T> class BinNode {
public:
BinNode(){leftChild=rightChild=NULL;}
~BinNode(){delete leftChild;delete rightChild;}
private:
T data;
BinNode <T> *leftChild;
BinNode <T> *rightChild;
};
