我有以下代码将节点插入树中。问题是代码不工作,没有编译错误,但输出不正确。代码如下:
#include <stdio.h>
struct node {
int data;
node *left;
node *right;
};
node * insertNode(node *root, int value) {
if(root == NULL) {
printf("%s\n", "root is null, making new node");
node * new_node = new node;
new_node->data = value;
new_node->left = NULL;
new_node->right = NULL;
root = new_node;
printf("%s\n", "root assigned to new node");
}
else {
if(root->data < value) {
printf("%s\n", "Right subtree");
insertNode(root->right, value);
} else {
printf("%s\n", "Left subtree");
insertNode(root->left, value);
}
}
return root;
}
void printTree(node *root) {
if(root != NULL) {
if(root->left != NULL) {
printTree(root->left);
}
printf("%d ", root->data);
if(root->right != NULL) {
printTree(root->right);
}
}
else {
printf("%s\n", "root is null");
return;
}
}
int main()
{
node *root = new node;
root->data = 1;
root->left = NULL;
root->right = NULL;
root = insertNode(root, 2);
printTree(root);
return 0;
}
我哪里错了?
答案 0 :(得分:2)
您忘记分配递归函数insertNode
的返回值。将insertNode(root->right, value)
更改为root->right = insertNode(root->right, value);
,将insertNode(root->left, value)
更改为root->left = insertNode(root->left, value);
。函数insertNode
的第一个参数只是输入参数,输出是您的返回值。像这样调整你的代码:
node * insertNode(node *root, int value) {
if( root == NULL ) {
printf("%s\n", "root is null, making new node");
node * new_node = new node;
new_node->data = value;
new_node->left = NULL;
new_node->right = NULL;
root = new_node;
printf("%s\n", "root assigned to new node");
}
else {
if( root->data < value ) {
printf("%s\n", "Right subtree");
root->right = insertNode( root->right, value );
// ^ assigne possibly new right node
} else {
printf("%s\n", "Left subtree");
root->left = insertNode( root->left, value );
// ^ assigne possibly new left node
}
}
return root;
}
另一个解决方案是更改函数insertNode
的签名并通过指针传递参数:
void insertNode(node **root, int value) {
// ^^ in and output parameter
if( *root == NULL ) {
printf("%s\n", "root is null, making new node");
node * new_node = new node;
new_node->data = value;
new_node->left = NULL;
new_node->right = NULL;
*root = new_node;
printf("%s\n", "root assigned to new node");
}
else {
if( (*root)->data < value ) {
printf("%s\n", "Right subtree");
insertNode( &((*root)->right), value );
} else {
printf("%s\n", "Left subtree");
insertNode( &((*root)->left), value );
}
}
}
int main()
{
node *root = new node;
root->data = 1;
root->left = NULL;
root->right = NULL;
insertNode( &root, 2 );
// ^
printTree(root);
return 0;
}
请注意,您永远不会删除已分配的节点。