当我尝试在下面的定义中访问(x->左)时,函数tdeleteLeft(x)中发生分段错误:
void BST::tdeleteLeft(Node* x){
if (x->left == NULL){
tdelete(x);
}
else{
Node* y;
y = max(x->left);
tdelete(x->left);
x = y;}
}
这是完整的程序:
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <iostream>
using namespace std;
class BST {
public:
typedef struct node {
int value;
struct node *left;
struct node *right;
node() {
left = NULL;
right = NULL;
}
}Node;
Node *root;
Node* i;
Node* y;
int z;
static int c;
int count();
void inc();
BST(int n);
void tdelete(Node* x);
Node* max(Node* x);
void remove_node(Node* x);
Node* min(Node* x);
void tdeleteLeft(Node* x);
void insert(Node* tree, int val);
};
int main ()
{
// create BST tree with n nodes
BST *tree = new BST(10);
clock_t t;
t = clock();
tree->remove_node(tree->root);
t = clock() - t;
cout << t << " clicks " << ((float)t)/CLOCKS_PER_SEC << "seconds).\n" << endl;
return 0;
}
BST::BST(int n){
c = 1;
z = 0;
Node *root = NULL;
for (int i=0; i<n; i++){
int rando = rand() % 10;
insert(root, rando);
}
cout << "created " << n << "-node BST" << endl;
}
int BST::c;
int BST::count(){
return c;
}
void BST::inc(){
c++;
}
BST::Node* BST::max(Node* x){
if (x->right == NULL){
return x;
}
else
return max(x->right);
}
BST::Node* BST::min(Node* x){
Node* i = x;
while (i->left !=NULL){
i = i->left;
}
return i ;
}
void BST::tdelete(Node* x){
if (x->right!=NULL){
tdelete(x->right);
}
if (x->left!=NULL){
tdelete(x->left);
}
delete(x);
}
void BST::tdeleteLeft(Node* x){
if (x->left == NULL){
tdelete(x);
}
else{
Node* y;
y = max(x->left);
tdelete(x->left);
x = y;}
}
void BST::remove_node(Node* x){
tdeleteLeft(x);
}
void BST::insert(Node *tree, int val){
if(tree==NULL){
BST::Node* tree = new BST::Node();
tree->left = NULL;
tree->right = NULL;
tree->value = val;
c++;
}
else{
if(c%2==0){
insert(tree->left, val);}
else
insert(tree->right, val);}
}
答案 0 :(得分:0)
首先,root
BST::BST(int)
的以下声明
BST::BST(int n){
c = 1;
z = 0;
Node *root = NULL; // <--- This defines a local variable which shadows BST::root
for (int i=0; i<n; i++){
...
shadows同名成员。相应地,tree->root
中的main
在调用构造函数后仍未初始化。
结果tree->remove_node(tree->root)
尝试删除未初始化指针的“左”节点,这会导致您正在观察的分段错误。要解决该问题,您需要删除root
变量的本地声明:
BST::BST(int n){
c = 1;
z = 0;
for (int i=0; i<n; i++){
...
然后你应该注意insert(root, rando)
不会更新调用者上下文中的root
变量,因为指针是按值传递的,因此分配的树节点变得无法访问。为防止这种情况,您可以使用以下命令返回更新的根节点:
Node* BST::insert(Node* tree, int val){
if(tree==NULL){
tree = new BST::Node(); // careful about shadowing the "tree" argument
...
}
else{
if(c%2==0){
tree->left = insert(tree->left, val);
}
else{
tree->right = insert(tree->right, val);
}
}
return tree;
}
你在构造函数中调用它是这样的:
BST::BST(int n){
c = 1;
z = 0;
for (int i=0; i<n; i++){
int rando = rand() % 10;
root = insert(root, rando);
}
}
或通过引用传递指针:
void BST::insert(Node*& tree, int val){
...
}